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ACSM's Guide to Exercise and Cancer Survivorship
Edited by Melinda L. Irwin and American College of Sports Medicine
208 Pages
ACSM’s Guide to Exercise and Cancer Survivorship presents the science behind the benefits of exercise for cancer survival and survivorship as well as the application of that science to the design or adaptation of exercise programs for cancer patients and survivors. Developed by the American College of Sports Medicine (ACSM), this authoritative reference offers the most current information for health and fitness professionals working with survivors of many types of cancers.
Dr. Melinda L. Irwin has assembled a team of the most respected experts in the field of exercise and cancer survivorship. With an emphasis on practical application, the text discusses the following:
• Incidence and prevalence of the most common cancers
• Common cancer treatments and side effects
• Benefits of exercise after a diagnosis of cancer
• Exercise testing, prescription, and programming
• Nutrition and weight management
• Counseling for health behavior change
• Injury prevention
• Program administration
This guide presents evidence-based information to assist health, fitness, and medical professionals in using exercise to help cancer survivors with recovery, rehabilitation, and reducing the risk of recurrence. Throughout the text, readers will find quick-reference Take-Home Messages that highlight key information and how it can be applied in practice. Chapters also include reproducible forms and questionnaires to facilitate the implementation of an exercise program with a new client or patient, such as physician’s permission forms, medical and cancer treatment history forms, weekly logs of exercise and energy levels, medication listings, and nutrition and goal-setting questionnaires.
In addition, ACSM’s Guide to Exercise and Cancer Survivorship discusses all of the job task analysis points tested in the ACSM/ACS Certified Cancer Exercise Trainer (CET) exam, making this the most complete resource available for health and fitness professionals studying to attain CET certification. Each chapter begins with a list of the CET exam points discussed in that chapter. A complete listing is also included in the appendix. As both an essential preparation text for certification and a practical reference, ACSM’s Guide to Exercise and Cancer Survivorship will increase health and fitness professionals’ knowledge of the benefits of exercise after a cancer diagnosis as well as the specifics of developing and adapting exercise programs to meet the unique needs of cancer survivors.
Evidence has shown that physical activity has numerous health benefits for cancer patients and survivors. More clinicians and oncologists are recommending exercise as a strategy for reducing the side effects of treatment, speeding recovery, and improving overall quality of life. In turn, cancer survivors are seeking health and fitness professionals with knowledge and experience to help them learn how to exercise safely within their capabilities. With ACSM’s Guide to Exercise and Cancer Survivorship, health and fitness professionals can provide safe exercise programs to help cancer survivors improve their health, take proactive steps toward preventing recurrences, and enhance their quality of life.
Chapter 1. Diagnosis and Treatment of Cancer
Larissa A. Korde, MD, MPH
Cancer Incidence and Survival
Cancer Biology
Cancer Staging
Cancer Screening and Diagnosis
Cancer Recurrence Warning Signs
Summary
References
Chapter 2. Side Effects and Persistent Effects of Cancer Surgery and Treatment
Tara Sanft, MD, and Melinda L. Irwin, PhD, MPH
Side Effects of Cancer Surgery and Treatment
Recurrence, New Primaries, and Second Cancers
Summary
References
Chapter 3. Lifestyle Factors Associated With Cancer Incidence, Recurrence, and Survival
Heather K. Neilson, MSc, and Christine M. Friedenreich, PhD
Effect of Body Weight
Effect of Exercise
Effect of Diet
Summary
References
Chapter 4. Benefits of Physical Activity After a Cancer Diagnosis
Kristin L. Campbell, BSc PT, PhD
Physiological Effects of Exercise Training
Psychological Benefits of Exercise Training
Cancer-Specific Exercise Issues by Body System
Effects of Cancer Medications or Treatments on Designing an Exercise Program
Summary
References
Chapter 5. Cardiorespiratory Fitness Testing in Clients Diagnosed With Cancer
Lee W. Jones, PhD, and Claudio Battaglini, PhD
Administration of Cardiorespiratory Fitness Testing
Exercise Testing Safety
Summary
References
Chapter 6. Exercise Prescription and Programming Adaptations: Based on Surgery, Treatment, and Side Effects
Kathryn Schmitz, PhD, MPH
Health Promotion and Risk of Disease Reduction
Exercise Prescription Alterations to Address Individual Needs
Benefits and Risks of Exercise and Exercise Training
Exercise Prescription Individualization
Acute and Chronic Adverse Effects of Treatment
Setting Goals
Sample Exercise Prescriptions
Summary
References
Chapter 7. Nutrition and Weight Management
Stephanie Martch, MS, RD, LD, and Wendy Demark-Wahnefried, PhD, RD
Diet in Cancer Prevention, Control, and Overall Health
Weight Status and Body Composition
Weight and Height Assessment
Energy Consumption and Cancer
Diet Composition and Nutrition Status
Complementary Alternative Medicine and Functional Foods
Dietary Supplements
Alcohol
Summary
References
Chapter 8. Health Behavior Change Counseling
Karen Basen-Engquist, PhD, MPH; Heidi Perkins, PhD; and Daniel C. Hughes, PhD
Effect of Cancer on Readiness to Exercise
Theory-Based Methods and Exercise
Translating Theory Into Practice
Summary
References
Chapter 9. Safety, Injury Prevention, and Emergency Procedures
Anna L. Schwartz, PhD, FNP, FAAN
Cancer-Specific Safety Considerations
Emergency Procedures
Documentation
Summary
References
Chapter 10. Program Administration
Carole M. Schneider, PhD
Designing a Cancer Rehabilitation Program
Cancer Rehabilitation Programs and Settings
Program Description and Operations
Policies and Procedures
Legal Issues and Documentation
Reimbursement Concerns
Community-Based Support
Summary
References
The American College of Sports Medicine (ACSM), founded in 1954, is the world’s largest sports medicine and exercise science organization with more than 45,000 national, regional, and international members and certified professionals in more than 90 countries. With professionals representing more than 70 occupations, ACSM offers a 360-degree view of sports medicine and exercise science. From academicians to students and from personal trainers to physicians, the association of sports medicine, exercise science, and health and fitness professionals is dedicated to helping people worldwide live longer, healthier lives through science, education, medicine, and policy.
About the Editor
Melinda L. Irwin, PhD, MPH, is an associate professor in the Yale School of Public Health and codirector of the cancer prevention and control research program at Yale Cancer Center. Dr. Irwin's research focuses on how exercise and weight influence cancer risk and survivorship. Dr. Irwin is the principal investigator of a number of research studies at Yale University and collaborates on various national projects and initiatives focused on exercise and cancer survivorship. She has received funding from the National Cancer Institute, American Cancer Society, Komen for the Cure, Lance Armstrong Foundation, and American Institute for Cancer Research and has published her research findings in top medical journals. Dr. Irwin also serves on various national advisory committees to develop consensus statements on physical activity, diet, weight control, and cancer prevention and control.
"Concise chapters cover descriptions of cancer to understanding how it doesn't need to be a limiting factor in exercise participation. The book does an excellent job of providing real-life examples and demonstrating how the recommendations can be implemented in everyday practice."
--Doody’s Book Review, 5-star review
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Effect of exercise on the risk of several cancer types
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.
Effect of Exercise
Considerable scientific evidence suggests that physical activity reduces the risk of several cancer types with the evidence classified as convincing or probable for colon, breast, and endometrial cancers; possible for prostate, ovarian, and lung cancers; and null or insufficient for other cancers.There is also increasing evidence that physical activity improves some health indicators and quality of life after diagnosis although there have not yet been any reported clinical trials on the effect of postdiagnosis physical activity on the risk of cancer recurrence or survival.Challenges of these trials include the possibility of group differences in prognostic factors and treatments; the stresses of diagnosis, treatment, and recovery on a patient's ability to exercise; and the need for a large trial to detect statistically significant differences between exercise and control groups.
The following sections review the scientific literature on cancer sites that have been studied most extensively in relation to physical activity. Epidemiologic research relating physical activity to ovarianand lung cancersare described elsewhere (see citations noted here). It is noteworthy that much of the epidemiologic evidence is based on studies that used questionnaires to estimate physical activity levels. Many factors must be considered when selecting a questionnaire,including its validity for the research question being asked.
Colon Cancer
The most consistent and strong evidence for a role of physical activity in cancer etiology exists for colon cancer. An average risk reduction of about 25 to 30% is observed in both men and women who undertake the highest level of assessed physical activity compared to the lowest level of activity in studies that have examined these associations(activity levels were not uniformly defined). These findings are likely to be independent of body weight changes. There is evidence for a dose-response effect with more benefit being observed for higher levels of activity, as defined in each study. These results have been observed in studies conducted in a variety of populations around the world, using varying methods for assessing physical activity and with various study designs.
Although 52 studies of physical activity and colon cancer have been identifiedsome aspects of this etiologic association remain unclear including whether the benefits of physical activity depend on menopausal hormone therapy use, dietary intake, or BMI. In addition, the time in life when physical activity is most beneficial for colon cancer prevention is unknown; greater risk reductions may result from higher activity levels over the lifetime as opposed to more recent activity.It is also unclear whether physical activity has a differential effect on various regions of the colon.64
Based on the overall evidence from studies of recreational activity, about 30 to 60 minutes per day of moderate- to vigorous-intensity physical activity may be needed to lower colon cancer risk significantly.An even greater benefit for colon cancer risk reduction may exist for vigorous-intensity activity,13 but the magnitude of this benefit is unclear.
Relatively recent research has been conducted on the role of leisure-time activity in improving colon cancer survival.Four cohort studies conducted by Meyerhardt and colleaguesall showed better survival among colorectal cancer survivors who were more physically active postdiagnosis. In addition, in the Melbourne Collaborative Cohort Study, prediagnosis exercise was associated with better disease-specific survival.
The largest prognostic study to date was conducted in 832 men and women with stage III colon cancer.In that study 18 to 26.9 MET-hours per week of postdiagnosis leisure-time activity lowered the risk of cancer recurrence or death by 49% compared with those who did less than 3 MET-hours per week. Furthermore, significant trends were found relating increasing activity levels to improved disease-free, recurrence-free, and overall survival. A minimum of 18 MET-hours per week of leisure activity improved disease-free survival rates regardless of sex, BMI, number of positive lymph nodes, chemotherapy type, age, or baseline performance status.
Breast Cancer
Extensive research has been conducted on the etiologic role of physical activity in relation to breast cancer risk, with the majority of studies concluding that women who are more physically active have a lower risk compared to sedentary women. Across 73 studies, the average risk reduction was about 25% for the highest versus the lowest activity categories compared,and there is consistent evidence of a dose-response effect, with greater risk decreases observed with higher levels of activity. All types of activity are beneficial, with somewhat stronger effects observed overall for recreational and household activity.As well, the effect appears to be significant more often in postmenopausal women and, on average, and is stronger in normal weight women, non-Caucasians, women without a family history of breast cancer, and women who are parous. Effects are also stronger for activity done over the lifetime or after menopause, activity of moderate or vigorous intensity, or activity of longer duration (hours per week).
Based on previous research, at least four hours per week of moderate- to vigorous-intensity activity may be necessary to reduce risk significantly. A few aspects of this association remain unclear, including whether the benefit of physical activity depends on the histologic type of the tumor, the hormone receptor status, and other molecular aspects.
The role of physical activity in breast cancer survival has been examined in 15 observational studies conducted thus far.Eight of these studies suggested that higher physical activity levels were associated with a significantly decreased risk of breast cancer mortalityor overall mortality,implying that physically active people with breast cancer may have improved prognosis with fewer recurrences and deaths compared with sedentary survivors. The largest prognostic studies to date were conducted in the Breast Cancer Family Registryand the Collaborative Women's Longevity Studywith each study enrolling more than 4,000 breast cancer survivors. The latter study found a 51% decrease in breast cancer mortality among the most physically active as well as evidence for a dose-response effect of decreasing the risk of breast cancer death with increasing levels of total recreational activity postdiagnosis.In the Breast Cancer Family Registry study, all-cause mortality was decreased by 23 to 29% in women who were recreationally active three years prediagnosis compared to inactive women, whereas no association was found with lifetime physical activity.
Endometrial Cancer
Twenty of the 25 published epidemiologic studiessuggest a protective effect from physical activity in endometrial cancer risk; no association was reported in five studies.Overall, evidence suggests about a 20 to 30% decreased risk for the most active versus the least active study participants; also, activity of light to moderate intensity may lower risk, whereas sitting time may increase risk.Despite these findings, recent reviews of this literaturehave emphasized the need for further research studies that have more detailed assessments of lifetime physical activity and that consider all types and parameters of activity. Furthermore, it remains somewhat unclear how independent this association is from BMI or whether this effect depends on menopausal hormone therapy use.
No observational studies have been published on the role of exercise in endometrial cancer survival, but one randomized controlled trial examined how a six-month intervention of lifestyle counseling could influence physical activity levels, dietary habits, weight loss, and quality of life in endometrial cancer survivors.This study was able to achieve more weight loss and increased exercise levels in the intervention group than in the control group and demonstrated that this type of lifestyle intervention is feasible and could result in sustained behavior change over a yearlong period.
Prostate Cancer
There is inconsistent evidence regarding the association between physical activity and prostate cancer, with about one third (16 out of 42) of the studies conducted thus far indicating a protective effect.The magnitude of the risk reduction is modest, on average around 9%,and there remains a lack of clarity on whether the benefit from physical activity varies according to other factors such as age, race, family history, and BMI. The effect of physical activity may also be more restricted to advanced prostate cancers. Some evidence is emerging that higher levels of lifetime physical activity may decrease prostate cancer risk.Both occupational and recreational activities have been associated with decreased prostate cancer risk.
The inconsistency across prostate cancer studies may be attributed to several factors. First, prostate cancer is a slow-growing tumor with a long latency period, and a large percentage of men die with evidence of undiagnosed prostate cancer. Therefore, some studies may have been unable to detect a difference in physical activity levels between the cancer patients and the “healthy” control populations because of latent, nonclinical prostate cancer among the controls. Second, healthier, physically active men may be more likely to be screened for prostate cancer, and hence more likely to be diagnosed, than less active men. As a result, some study populations might not have accurately reflected the general population of cancer patients, and true risk reductions were attenuated. Finally, it has been hypothesizedthat studies including a greater proportion of screen-detected, early-stage prostate cancer cases might reveal weaker associations between physical activity and prostate cancer risk than studies of advanced prostate cancer. A study by Littman and colleaguesfound a strong inverse association between physical activity and prostate cancer risk in men with no history of recent PSA testing, but no association was found in men with a history of recent PSA testing. Another studyshowed no difference in risk based on PSA screening history, casting doubt on this hypothesis.
Only one observational study has reported on physical activity and prostate cancer survival.In that study of 2,705 nonmetastatic prostate cancer survivors from the Health Professionals Follow-Up Study, men who engaged in leisure-time physical activity postdiagnosis had significantly lower risks of all-cause and prostate cancer mortality; significant trends were noted, with increasing MET-hours per week corresponding with greater reductions in risk. Men reporting at least three hours per week of vigorous activity (versus less than one hour per week) had a 61% lower risk of death from prostate cancer.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Diet affects the risk of cancer
An unhealthy diet could account for up to 30% of all cancers in developing countries and perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer.
Effect of Diet
An unhealthy diet could account for up to 30% of all cancers in developing countriesand perhaps 35% of cancer deaths in the United States. Hence, along with tobacco use, diet is one of the most important modifiable risk factors for cancer. Given the diverse and complex nature of the human diet, however, it is also one of the most difficult factors to study in large human populations. Numerous instruments for dietary assessment have been developed and validated.As in physical activity assessment, the choice of instrument depends largely on the intended purpose. A vast body of epidemiologic research has addressed a wide array of research questions related to cancer and diet in an attempt to disentangle individual dietary effects. Here we highlight some of the strongest associations identified thus far,although more associations will undoubtedly emerge in the future.
Sugar, Fast Foods, and Other Energy-Dense Foods
High-calorie foods and drinks are suspected risk factors for cancer given their contributions to weight gain, overweight, and obesity. The risks deriving from specific aspects of an energy-dense diet, however, are not as clear. Foods containing high amounts of sugar, for example, may be associated with increased colorectal cancer risk, and biologic mechanisms have been proposed, but the overall evidence in humans is currently limited and merely suggestive.
In terms of fat intake, evidence from a substantial number of human studies has provided only limited, but suggestive evidence for increased risk of cancers of the lung, breast, colorectum,and possibly prostate.Despite plausible biologic mechanisms for these cancers, the overall findings surrounding fat intake and cancer incidence are inconsistent. Notably, dietary fat has been studied in relation to breast cancer recurrence and survival in two large randomized controlled trials. Findings from the Women's Intervention Nutrition Studyand the Women's Healthy Eating and Living studyhave suggested limited prognostic gain from lowering dietary fat, although there may be some decrease in recurrence rates for certain subgroups
of postmenopausal women. More limited evidence suggests that the aggressiveness of prostate tumors and deaths from prostate cancer may be related to higher total and saturated fat intakes.
Fruits and Vegetables
A plant-based diet rich in fruits, vegetables, and whole grains is continually recommended for the prevention of various cancers.In a comprehensive review of published literature on this subject, a variety of fruits and vegetables appeared likely to preventcancer, although the evidence was not fully convincing (see table 3.3).
Compared to cancer incidence, far fewer studies have examined fruit and vegetable intake in relation to cancer prognosis. Very limited data support a decreased risk of recurrence or progression of prostate cancer, for example, with higher intake of tomatoes or lycopene.Vegetable intake has been linked to longer survival from ovarian cancerand advanced lung cancer,but again, these findings are very preliminary. The effects on breast cancer prognosis are also unclear.In the Women's Healthy Eating and Living randomized controlled trial of breast cancer patients, long-term adoption of a low-fat diet high in fruits, vegetables, and fiber had no effect on breast cancer recurrence or survival.
Fruits and vegetables could prevent cancer through multiple, interrelated mechanisms. Promotion of a healthy body weight, prevention of oxidative stress and DNA damage, and the ability to alter the activities of carcinogen-activating enzymes are just a few possible mediating pathways to prevention. Higher intake may also favorably alter immune function, inflammation, and cellular growth.
Fiber
According to one international report on cancer prevention,a diet high in fiber may well reduce the risk of colorectal cancer. Yet, at least one pooled analysis of research on this subject found no effect from fiber beyond the effects of other dietary risk factors.Part of the difficulty in studying fiber intake in humans may be that intake is too low to observe any benefit.The Polyp Prevention Trial, conducted in the United States, explored the effect of increasing dietary fiber intake over four years (and also lowering fat and increasing fruit and vegetable intakes) in people who had previously experienced one or more colorectal adenomas. Adenoma recurrence was significantly lowered among the most compliant study participants,implying that a high-fiber diet may also lower the risk of colorectal cancer recurrences.
The reasons that fiber may be protective are unclear, but several mechanisms have been proposed.High fiber intake favorably alters the quality of the feces by diluting its contents, increasing its weight, and shortening transit time through the colon. The outcome of these effects is decreased contact between potential fecal carcinogens and colonic cells. As well, fiber fermentation products (e.g., butyrate) produced in the gut can help promote healthy cellular growth. Furthermore, intakes of fiber and folate are correlated, and hence, the observed effects may actually be from folate.
Red Meat and Processed Meat
There is convincing evidence that consumption of red meat and processed meat (i.e., preserved by smoking, curing, salting, or with preservatives) increases the risk of colorectal cancer.Very few studies, however, have examined the effect of diet on colorectal cancer recurrence and survivorship. In one follow-up study of patients with stage III colon cancer, postdiagnosis intake of a “Western diet” (high intake of red and processed meats, sweets, French fries, and refined grains) was associated with higher risks of recurrence and death, whereas a “prudent diet” (fruits, vegetables, legumes, fish, poultry, and whole grains) was not associated with an increased risk.Whether these findings are attributable to meat intake specifically, however, is unknown.
Red and processed meats might increase cancer risk because potentially carcinogenic N-nitroso compounds are formed in the stomach and gut following their ingestion. Cooking at high temperatures produces potentially carcinogenic by-products, and the heme iron content of meats may also promote DNA damage and cancer in the colon. Moreover, processed meats are high in salt, which also encourages the formation of N-nitroso compounds. In addition, higher meat consumption may coincide with low intakes of fruits, vegetables, and fiber, which may decrease cancer risk.
Alcohol
There is now a wealth of convincing evidencethat total alcohol intake, irrespective of the source, increases the risk of cancers of the mouth, pharynx, larynx, esophagus, colorectum (in men)and breast in both pre- and postmenopausal women.With respect to breast cancer, the increased risk from alcohol appears to be the most elevated in women with low folate intake.It is less convincing, but still probable, that alcohol consumption increases the risk of liver cancer and of colorectal cancer in women. Alcohol in small quantities does not appear to prevent cancer as it does cardiovascular disease.The effect of alcohol intake on cancer prognosis has been studied in relation to breast cancer; however, the effect remains uncertain. Alcohol intake has not been associated with breast cancer recurrence or overall survival in most studies of women diagnosed with breast cancer.
Alcohol may increase cancer risk via multiple pathways.Some of its metabolites and by-
products, for example, may be carcinogenic. Alcohol also acts as a solvent, which facilitates the entry of other cancer-causing compounds (e.g., as found in tobacco) into cells. Hence, for certain cancers, the combined cancer-causing effects of alcohol and tobacco are worse than they would be for either substance alone. Furthermore, alcohol may indirectly alter normal cell cycles, affect the metabolism of other carcinogens, increase circulating hormone levels, and reduce folate levels.
Salt
Total salt intake and the intake of salted and salty foods are probably associated with stomach cancer, and intake of Cantonese-style salted fish appears to increase the risk of nasopharyngeal cancer.Salt intake could plausibly cause stomach cancer by damaging the stomach lining, increasing the formation of N-nitroso compounds, which are potentially carcinogenic, or interacting with other carcinogens. It is also hypothesized that salt intake and Heliobacter pylori infection might act synergistically to increase risk. Salted fish may increase the risk of cancer of the nasopharynx because of its N-nitrosamine content.
Dietary Supplements
In their report on diet and cancer prevention, the World Cancer Research Fund and the American Institute for Cancer Researchdo not recommend dietary supplements for the purpose of preventing cancer. Instead, they recommend that proper nutrition be attained through the intake of foods alone. Although evidence suggests that some supplement use may help prevent cancer, high doses can actually causecancer in certain subgroups of the population. For example, convincing evidence supports a causal role for high-dose beta-carotene supplement use in lung cancer, depending on smoking status and genetics.The American Cancer Society similarly advises cancer survivors to avoid very high doses of vitamins, minerals, and other dietary supplements; they state that although low doses may be useful, they should only be taken with advice from a health care provider.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Muscular strength and endurance in cancer survivors
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors, with the majority of research being in those with breast cancer, prostate cancer, and head and neck cancer.
Muscular Strength and Endurance
Resistance exercise training has been effective in improving muscular strength and endurance in cancer survivors,with the majority of research being in those with breast cancer,prostate cancer,and head and neck cancer.Muscular strength has been measured as 1-repetition maximum (1RM) or 6- to 7-repetition maximum to estimate 1RM. Muscular endurance has been measured as the number of repetitions of a certain weight in a set time. Assessing baseline muscular strength and endurance is important for developing the most appropriate and effective prescription for cancer survivors.
Research studies with cancer survivors have used a variety of resistance prescriptions,as follows:
- Frequency: One to five sessions per week (primarily two or three)
- Number of exercises: Varied numbers involving large muscle groups (primarily five to nine)
- Sets: One to three sets
- Repetitions: 8 to 12 reps
- Intensity: 25 to 85% of 1RM
- Duration of program: 3 to 52 weeks
The 2010 ACSM roundtable guidelines for resistance training exercise for cancer survivors are also consistent with the 2008 U.S. DHHS “Physical Activity Guidelines for Americans.”Cancer survivors are encouraged to meet the U.S. DHHS guidelines of two or three weekly sessions that include exercises for the major muscle groups,as able.
Strong evidence of the benefit of resistance training has been reported in breast cancer and prostate survivors during and following cancer treatment.1 The role of resistance training following surgery for breast cancer has been controversial; traditionally, practitioners have advised people not to lift more than 10 pounds (4.5 kg) and to limit repetitive upper-extremity activities. These limitations were aimed at reducing the risk of developing upper-extremity lymphedema, swelling that can affect the arm and trunk following breast cancer surgery and treatment. Results from recent research have suggested that progressive resistance training improves muscular strength, muscular endurance, and functional ability, without increasing the risk of developing upper-extremity lymphedema or exacerbating preexisting lymphedema.
Schmitz and colleaguesstudied breast cancer survivors with preexisting lymphedema. The exercise group had an increase in strength, measured as 1RM, of 29.4% for the bench press (versus 4.1% in controls) and 32.5% for the leg press (versus 7.6% in controls). The exercise group reported a significant improvement in lymphedema symptoms. Also, exacerbations of lymphedema were nominal in the exercise group, which also had fewer exacerbations compared to the control group. The key message stressed in this study was adhering to proper form and progressing the exercises slowly. To achieve this, the study included supervision by trained instructors for the first 13 weeks. Also, the intensity started low and progressed slowly by the smallest increment to reduce the risks of worsening lymphedema. In addition, participants wore compression sleeves during their resistance exercise sessions, and symptoms of worsening lymphedema (i.e., swelling, feelings of heaviness) were closely monitored.
Resistance training has also been encouraged for prostate cancer survivors undergoing androgen deprivation therapy, which lowers testosterone levels. The treatment-associated reduction in muscle mass and muscle strength can compromise physical function, particularly in older men.In a study that compared a 12-week resistance training program and a usual care group during ADT treatment, the exercise group had a significant increase in upper- and lower-body muscular strength (1RM) and endurance (number of repetitions of 70% 1RM) compared to the control group, 36 with an 11% improvement in 1RM chest press (versus 1% in controls) and 37% improvement in the 1RM leg press (versus 7% in controls).
Resistance training has also been studied in head and neck cancer survivors. Resistance training in this population may be particularly important because of the associated shoulder dysfunction, which is a well-recognized complication of the neck dissection surgeries commonly used. The shoulder dysfunction is due to damage to or resection of the spinal accessory nerves and surrounding muscles, such as the trapezius muscle. A small randomized controlled trial compared a 12-week standard care program that included range-of-motion, stretching, and shoulder-strengthening exercises with elastic resistance bands with a 12-week progressive resistance program based on individual baseline strength testing. Both groups improved muscular strength and endurance, but the individualized, progressive program resulted in greater improvements in 1RM for the seated row (37% versus 15% in the standard care group) and the chest press (45% versus 24% in the standard care group).
Timing
The majority of resistance training programs for people with cancer have been undertaken following cancer treatment and have reported benefits.However, research on the benefits of resistance training during chemotherapy treatment is limited. During chemotherapy, an improvement in strength was reported in breast cancer survivors who were randomized to a resistance exercise program compared to those randomized to an aerobic exercise program or control group (the only group to maintain their usual lifestyle).In addition, the resistance group in this study also had a better chemotherapy completion rate than the aerobic exercise or control group did. A better chemotherapy completion rate means that people were more likely to receive their prescribed chemotherapy dose on schedule, instead of experiencing the delays commonly seen with chemotherapy. A better chemotherapy completion rate is an outcome that may be of particular interest to the clinical oncology community (i.e., oncologists) because delivery of the prescribed chemotherapy dose is linked to improved clinical outcomes. Improvements in upper- and lower-body strength were also noted in prostate cancer survivors who took part in a resistance program during radiation therapyand during androgen deprivation therapy.
Specificity of Training
As with aerobic interventions, issues with specificity also exist for resistance interventions. Baseline testing has not been used universally. A generic approach to prescribing resistance exercise that does not take baseline strength into account may result in an exercise prescription that is too easy (and therefore results in less improvement) or too hard (limiting improvement and possibility increasing the risk of injury).
The 1-repetition maximum (1RM) test has been employed during recent exercise studies with breast, prostate, and head and neck cancer survivors to determine the appropriate exercise prescription for program.This information has then been used to develop an exercise prescription in a variety of ways. The initial intensity for head and neck cancer survivors was set at 25 to 30% of 1RM and progressed to 60 to 70% of 1RM. The protocol included both double- and single-limb (arm) exercises, because strength was disproportionally reduced on the treatment side as a result of surgery or radiation.32 This study included both men and women, making an individualized approach even more important than in studies of a single sex. For breast cancer survivors with or without lymphedema, the goal of the program by Schmitz and colleagues35 was to progress slowly to avoid acute injury to the arm. Damage to the arm has been suggested as a risk factor for lymphedema (see chapter 6). The authors did not set an upper limit for resistance.
Supervision is another key feature in achieving specificity of resistance training. Supervision initially or for the entire study can ensure that clients use proper form and an appropriate progression. Home-based programs are more difficult to monitor for proper form or appropriate progression of resistance, which may limit clients' gains in strength and endurance.
Finally, adherence and compliance to the prescribed intensity and progression have not been well documented in the literature, which limits the ability to determine the overall expected effect of resistance programs for cancer survivors. Further research is needed to continue the development of feasible and effective resistance programs for cancer survivors.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Cancer treatments affect all elements of fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance.
Effects of Treatment on All Elements of Fitness
The elements of fitness include agility, speed, coordination, flexibility, strength, and endurance. Before clearing a cancer survivor for participation in a specific program or developing an individualized exercise prescription for that person, the fitness professional must understand what the exercise program will require of the survivor with regard to each of these elements, and whether the survivor is capable of participating in that component of exercise. For example, if a specific mode of aerobic exercise requires the ability to sustain an intensity level of 7 to 9 METS, but the maximal aerobic capacity of the client is 8 METs, it would not be appropriate to prescribe that particular mode of aerobic exercise. It is important to match the programming with the ability of the client.
One particular challenge in working with the cancer survivorship population is the interaction of aging with cancer. Cancer is more likely to occur in older people. Also, those who are diagnosed with cancer seem to experience an acceleration of functional aging. However, a healthy, fit 70-year-old diagnosed with early-stage cancer that requires minimal surgery, no chemotherapy, and a short round of radiation therapy could be ready to join a masters running club three months after treatment. By contrast, a sedentary, overweight, diabetic 40-year-old diagnosed with stage III colon cancer that requires extensive surgical resection, an external ostomy (e.g., a bag outside the body that stores waste), and a long bout of chemotherapy might need physical therapy just to return to functional mobility and independent living prior to beginning a basic walking and weight training program. The point is to evaluate survivors according to their current abilities and prescribe appropriate exercise programming according to the findings.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.
Fruits and vegetables relation to cancer reduction
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management.
Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
Pesticides
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
Organic Foods
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.
Read more from ACSM's Guide to Exercise and Cancer Survivorship by American College of Sports Medicine.