The Role of Exercise for Patients With Cancer
Primary Care Update
Brief Summaries for Clinical Practice
Exercise has consistently been shown to improve the quality of life and psychological well-being of the general population. Despite these well-documented health benefits of regular exercise, more than 50% of the population does not engage in regular physical activity.1
In view of recent media attention focusing on obesity, more physicians have begun to address the topic of exercise with their patients. One population that is typically overlooked, however, is patients with cancer, even as a growing body of research has demonstrated the beneficial effects of exercise for this group. Physicians must become more aware of these data and of the role that exercise can serve. To this end, the American Cancer Society (ACS) and the American College of Sports Medicine have issued recommendations on regular physical activity for cancer survivors.2
Cancer is currently the second leading cause of death for adults, with more than 550,000 cases occurring annually.3 The 5 most common types of cancer in the United States are skin, breast, colorectal, prostate, and lung cancer.4
Early detection methods and improvements in treatment and recovery have resulted in a dramatic increase in the number of cancer survivors, which total 10.1 million.5 In addition, the life-span of cancer survivors is increasing; 62% of patients with cancer have extended the length of their recovery and live more than 5 years after their diagnosis. In fact, in as short as a 9-year period (1983 to 1992), the 5-year survival rate for patients with prostate cancer and breast cancer increased from 78% to 86% and from 75% to 97%, respectively.6 Furthermore, the number of cancer survivors is expected to double over the next 50 years as research progresses and physicians translate the latest research findings to the clinical management of their patients.4
CANCER SURVIVORS
A cancer survivor is anyone who has been diagnosed with cancer and undergone successful treatment for it. Therefore, the spectrum of cancer survival includes treatment, recovery, and life after recovery. Cancer treatments can result in a variety of psychological and physiologic maladies, including decreased quality of life, fatigue, nausea, malnutrition, loss of lean body mass, sleep disturbance, and depression. The goal of physical activity during cancer treatment and recovery is to return patients to their normal physical and psychological function, with an emphasis on maintaining strength, function, and endurance.7
An increasing number of supportive studies demonstrate the potential impact of exercise regimens on enhanced outcome variables and quality of life of cancer survivors. In an evidence report on the effectiveness of exercise in patients with cancer, the Agency for Healthcare Research and Quality reviewed 24 studies that assessed a wide variety of outcomes in patients with cancer.8 Approximately 50% of those studies measured cardiovascular fitness and fatigue as primary outcomes; other variables included depression, quality of life, and immune parameters.
The results revealed that patients who participated in exercise programs demonstrated 100% improvement in assessments of strength, flexibility, fatigue/tiredness, confusion, difficulty sleeping, self-esteem, psychosocial outcomes, body size, vigor and vitality, immune function, and mental health quality of life.8 Although the precise mechanism of the benefit remains to be determined, exercise likely improves immune function as well as regulates metabolic hormones, endogenous sex hormones, and growth factors. The authors concluded that physical activity is safe for cancer survivors and is beneficial for physiologic and psychosocial well-being.
Despite these findings, and the mounting evidence demonstrating a clear benefit for patients with cancer who incorporate exercise in their daily regimen, many physicians hesitate to prescribe exercise as part of a patient’s treatment, possibly because they lack sufficient knowledge to guide their patients or fear their patients are too fragile to undergo exercise. Moreover, patients may be apprehensive to initiate an exercise regimen without guidance or recommendations from their physicians. In addition, many patients are likely fatigued, understand their bodies are weak from disease and treatment, and are fearful about doing anything that they believe might negatively affect their body or symptoms further. The truth is, however, that in most cases, the benefits of exercise far exceed any risks.
BENEFITS OF EXERCISE FOR PATIENTS WITH CANCER
Virtually all patients with cancer can benefit from rehabilitation and exercise regimens, although most studies have focused on patients with breast, colon, or prostate cancer. The particular exercise prescription will differ depending on the type of treatment, type of cancer (eg, lung cancer versus skin cancer), and the stage of treatment or remission involved. For example, some patients may have disease-specific limitations, such as the growth of a tumor that directly affects the musculoskeletal system or a brain tumor that produces dizziness.
Improvement in quality of life. The negative effects associated with cancer treatments affect a patient’s quality of life. For example, during cancer treatment, anxiety and depressive symptoms are common.9 One study suggested that approximately 25% of patients with cancer will show symptoms of depression.10 In addition, 30% to 60% of patients with cancer will experience sleep disturbances.11 Furthermore, quality of life is likely to suffer in response to fatigue, nausea, loss of appetite, and other disorders.
Burnham and Wilcox7 found that a 10-week program of low- or moderate-intensity aerobic exercise was effective in improving both physical and psychological function in 21 men and women with cancer who began the regimen at least 2 months after completing treatment. The patients were matched for aerobic capacity and assigned to receive either low-intensity (25% to 35% of heart rate reserve) or moderate-intensity aerobic exercise (40% to 50% of heart rate reserve). To measure psychological function, the patients completed the Quality of Life Index for Cancer Patients and the Linear Analog Self-Assessment, which measures fatigue, anxiety, confusion, depression, energy, and anger.12 A number of physiologic assessments were also made, including body composition, flexibility, and peak aerobic capacity.
After 10 weeks, the patients demonstrated significant improvements in body composition, lower-body flexibility, aerobic capacity, and quality of life. Therefore, even low- or moderate-intensity exercise programs can be a sufficient stimulus to promote improvements in the psychological and physiologic well-being of patients with cancer.
Decrease in fatigue. Fatigue is often cited as the most common morbidity associated with cancer treatments and recovery. Schneider and colleagues13 suggested as many as 96% of patients experience fatigue and that this percentage increases with the length of treatment and chemotherapy sessions. Cancer survivors commonly report fatigue even during remission, and very often, their physician’s primary prescription for this symptom is rest. In addition to fatigue, a common adverse effect of treatment is extreme muscle wasting due to loss of appetite, nausea, and other adverse effects. Therefore, although the recommendation to rest for alleviating fatigue appears sensible, it may actually exacerbate the problem. Over time, physical inactivity will worsen fatigue because of the resultant muscle atrophy, decreased aerobic capacity, decreased functional capacity, and progressive inability to perform the daily activities of living.
Some studies have shown that aerobic exercise may be successful when prescribed as therapy for primary fatigue in patients with cancer.14 In a review study, Stricker and colleagues15 concluded that all patients with cancer should be encouraged to maintain an optimum level of physical activity during and after cancer treatment.
Decrease in nausea and malnutrition. Nausea is a common adverse effect of radiation and chemotherapy. Aside from the discomfort of nausea itself, nausea increases the risk of malnutrition and decreases the likelihood of lean body mass preservation. Winningham and MacVicar16 assessed the effects of a 10-week aerobic exercise program on nausea in patients undergoing chemotherapy for breast cancer. This study examined 3 patient groups: those who underwent aerobic exercise 3 days per week, those who underwent supervised flexibility training once weekly, and a control group. At the conclusion of the study, patients who participated in aerobic exercise demonstrated a significantly greater reduction in nausea symptoms than either the flexibility exercise or control groups.
Lean body mass preservation. Another common morbidity of cancer treatment is muscle atrophy, which is often caused by a lack of appetite, nausea, and fatigue. Each of these adverse effects leads to a decrease in energy intake and physical activity, which, in turn, contributes to the loss of lean body mass, thus precipitating a downward spiral of negative events that decrease a patient’s overall quality of life. Prostate cancer is of particular concern, as the common treatment for this disease is androgen deprivation therapy, which has been shown to negatively affect body composition (producing fat gain and loss of lean body mass) as well as increase the risk of osteoporosis.17
Segal and colleagues18 studied 155 men with prostate cancer who were scheduled to receive androgen deprivation therapy. The patients were randomly assigned to either an intervention group or a wait list control group. The men in the intervention group participated in a resistance exercise program 3 days per week for 12 weeks. The outcomes variables measured included both psychological and physiologic variables such as fatigue, quality of life, upper body and lower body muscular fitness, body weight, body mass index, waist circumference, and body composition. After 12 weeks, men in the intervention group reported less fatigue during their activities of daily living and a higher quality of life than those in the wait list control group. Moreover, the resistance-trained men showed significantly greater levels of upper and lower body muscular fitness. There were no significant differences in body weight, body mass index, waist circumference, or body composition.
CURRENT EXERCISE RECOMMENDATIONS FOR PATIENTS WITH CANCER
Individual situations vary, depending on the type of cancer, length of treatment, and other factors, but the most strongly consistent evidence is for enhanced cardiorespiratory fitness and reduced fatigue. The evidence report by the Agency for Healthcare Research and Quality suggests the exercise regimen most likely to produce positive outcomes in cancer survivors is moderate to vigorous intensity aerobic activity performed on 3 or more days per week for 10 to 60 minutes per session.8 Although this is a very broad range, research has not identified the potential benefits of more specific recommendations. Furthermore, it is unclear whether exercise produces a “dose-response” effect according to the level of activity or whether increasing activity negatively influences health outcomes.
As noted earlier, both the ACS and the American College of Sports Medicine have determined specific exercise recommendations for patients with cancer (Table 1).2 The ACS recommends that cancer survivors perform regular physical activity with the goal of maintaining a healthy body weight and reducing the risk of recurrence and of other common chronic diseases.
For example, if a patient is actively undergoing chemotherapy, it is vital that the clinician who is prescribing exercise also ensures the patient’s general health status is assessed before each exercise session. Exercise can be appropriate for persons with cancer who are otherwise healthy, but there are also a number of contraindications that would preclude participation in exercise (Table 2).2
EXERCISE PRESCRIPTION
It is critical for patients to talk with their personal physicians before starting any exercise program and for clinicians to discuss specific exercise guidelines with their patients. Currently, there are no guidelines suggesting a specific training regimen for patients with cancer or that explain how exercise activity should be determined according to the type of cancer, stage of recovery, or particular treatment modality involved. It is also important to discuss with otherwise healthy patients the benefits of other behaviors, in addition to exercise, in preventing cancer. Exercise is just one of a number of health behaviors, such as following a healthy diet, practicing weight control, and not smoking, that have been demonstrated to reduce the risk of cancer.
CANCER PREVENTION THROUGH EXERCISE
Obesity has been linked to an increased risk of the development of numerous types of cancer. The ACS estimates that overweight is a factor in about 15% of annual cancer deaths. Obese men and women are more than twice as likely as normal weight men to develop colon cancer. In addition, a postmenopausal woman’s risk of breast cancer increases by 30% if she is overweight and by 50% if she is obese. An overweight woman also has a 200% higher risk of developing endometrial cancer, and an obese woman’s risk increases nearly 500%. The connection between “hormonally based” cancers, in particular, such as breast and prostate cancer, is that exercise modulates endogenous hormones in the body. Moreover, it is well established that exercise is crucial for preventing weight gain and maintaining weight loss and that extra body weight itself can modulate endogenous hormones. In breast cancer, for example, endogenous and exogenous hormones can stimulate tumor growth; since exercise affects hormonal regulation, it may help control the rate of tumors either independently or indirectly through weight loss. Therefore, the importance of exercise in reducing weight cannot be overemphasized.
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