Exercise During and After Cancer Treatment
By Dónal P. O'Mathùna, PhD, Senior Lecturer in Ethics, Decision-Making & Evidence, School of Nursing and Human Sciences, Dublin City University, Ireland. Dr. O'Mathùna reports no financial relationships relevant to this field of study.
As of 2010, about 14 million cancer survivors were living in the United States, with the number projected to increase to 18 million by 2020.1 All people diagnosed with cancer are considered cancer survivors for the rest of their lives.2 As cancer treatments become more successful physiologically, more attention is being given to survivors' quality of life during and after treatment. Many cancer survivors are highly motivated to seek information about lifestyle factors that may influence their recovery and long-term quality of life.3 This includes the role of physical activity and exercise.
Various cancer treatments may have adverse effects that exercise theoretically could counteract, including pain, fatigue, impaired cardiorespiratory capacity, reduced quality of life, and suppressed immune function.4 However, rates of exercise decline considerably during chemotherapy and may not return to prediagnosis levels when treatment is concluded.3 A single-blind, randomized, controlled trial (RCT) found that an oncologist's 30-second verbal recommendation to exercise led to breast cancer patients significantly increasing their levels of exercise.3 The evidence to support such recommendations will be reviewed here. This evidence base has been growing rapidly, leading to new clinical guidelines from the American College of Sports Medicine (ACSM) in 20105 and from the American Cancer Society (ACS) in 2012.2
Background
Research on exercise and cancer is challenging to review because it involves many variables. Studies have focused on patients with many different cancer types, and at various stages of diagnosis and treatment. Many different activity and exercise regimens have been studied, and at least 60 diverse outcomes measured.6 Various study designs have been used, and carried out with varying levels of methodological rigor.
All these factors lead to complexity and variability in the design of research studies and the interpretation of their results. Such factors must be taken into account when making recommendations for individual patients and survivors.
Mechanism of Impact
Exercise can counteract some of the symptoms caused by cancer and some of the adverse effects associated with treatment. These can include unintended loss or gain of body weight, loss of muscle mass, nausea, vomiting, and difficulties eating or digesting food.2 Mood changes, fatigue, and other psychological disturbances frequently occur and may be affected by exercise. Cancer or its treatment may require periods of rest or bed rest, which can result in reduced fitness, endurance, or muscle strength that exercise at a later time could counteract. In addition, there is growing interest in the role exercise may play in preventing cancer recurrence and improving long-term survival.
Clinical Studies
An increasing number of studies have found that exercise is feasible and safe while patients are undergoing chemotherapy. Although many observational studies have been conducted, a growing number of RCTs have measured specific outcomes. A 2005 meta-analysis of this topic was updated in 2010 and found three times as many studies were now available for review.6 A wide range of outcomes have been measured, as can be seen in Table 1.
General physical activity, aerobic exercise, and resistance training have consistently shown benefits in outcomes including cardiopulmonary fitness, muscle strength, body composition, and balance.2 Exercise has also been shown to improve quality-of-life outcomes, such as fatigue, sleep quality, depression, and self-esteem. For example, one meta-analysis identified 78 studies examining the impact of exercise on quality-of-life outcomes in cancer survivors.7 About half the studies involved breast cancer survivors. Overall, the exercise groups reported significantly higher quality-of-life scores than the comparison group, whether this was measured in pre-post studies or against a control group. The effect size was larger at the long-term follow-up assessment (0.35; 95% confidence interval [CI], 0.27-0.44) than immediately after the exercise intervention stopped (0.24; 95% CI 0.20-0.28). Subgroup analysis showed that interventions with small amounts of aerobic exercise (like short walks) were associated with little or no quality-of-life change, while those with longer, larger amounts of aerobic activity (like moderately intense cycling) led to significant quality-of-life improvement. However, many of the studies provided few details about the exercise interventions.
Another meta-analysis examined the impact of exercise interventions on cancer-related fatigue.8 This review identified 44 studies of various designs involving 3254 survivors with different cancer types. Exercise interventions were used that varied in type, intensity, and duration. Overall, the cancer survivors in the exercise groups had greater reductions in fatigue levels (0.31; 95% CI, 0.22-0.40). The improvement in fatigue levels was significantly related to exercise intensity (P = 0.01) and was greater among older cancer survivors (P = 0.04).
Research into the impact of physical activity on cancer disease outcomes and secondary cancer prevention is a relatively new and rapidly growing area. A 2012 systematic review found that almost all controlled studies had been published since 2000, and all were case-control or cohort studies.1 The first RCT of a physical activity intervention where overall and disease-free survival are primary outcomes began recruiting subjects (colon cancer survivors) in 2009.1
Prospective, observational studies have found that physical activity after cancer diagnosis is associated with reduced risk of cancer recurrence and improved mortality with several types of cancers, including breast, colorectal, prostate, and ovarian.2 For example, a 2011 meta-analysis of six studies involving more than 12,000 breast cancer survivors found that post-diagnosis physical activity reduced breast cancer deaths by 34% (95% CI, 0.57-0.77, P < 0.00001), all-cause mortality by 41% (95% CI, 0.53-0.65, P < 0.00001), and disease recurrence by 24% (95% CI, 0.66-0.87, P = 0.00001).9 A more recent systematic review identified 43 studies in this area, with 27 being observational studies of cancer-related outcomes, five being observational studies involving cancer biomarkers, and 11 being RCTs measuring cancer biomarkers.1 The studies varied considerably in design, interventions, and outcomes. However, the reviewers concluded that "there is fairly consistent evidence that physical activity either before or after breast cancer diagnosis is associated with a reduction in both breast cancer-specific mortality and overall mortality."1 Other cancers have been studied much less frequently, but the results similarly find that physical activity is associated with improvements in all-cause and cancer-specific mortality. RCTs measuring biomarkers suggest that exercise may have beneficial effects on insulin and IGF in breast cancer survivors, and on C-reactive protein and natural killer cells in cancer survivors.1
Adverse Effects
Many of the RCTs and systematic reviews have explicitly collected data on adverse effects and concluded that exercise among cancer survivors is safe. For example, the ACSM guidelines gave the evidence for safety an A rating, defined as "overwhelming data from randomized controlled trials."5 One particular area of concern is lymphedema, a common adverse effect of breast cancer treatment. Women historically have been discouraged from upper body exercise for fear of exacerbating lymphedema after axillary lymph node removal or radiation. However, seven RCTs all have shown that upper body aerobic or resistance training does not lead to the development or worsening of lymphedema.5 These studies typically involve a supervised exercise program that gradually increases in intensity over 8 weeks with the women wearing a compression garment.10
Although exercise is not contraindicated for most cancer patients, particular individuals may be at higher risk of adverse effects. The ACS guidelines include some cautions.2 Cancer survivors:
- with severe anemia should delay exercise beyond activities of daily living until the anemia is improved.
- with compromised immune function should avoid exercising in public until their white cell count returns to safe levels.
- with severe fatigue from therapy should approach exercise cautiously.
- undergoing radiation should avoid chlorinated swimming pools.
- with indwelling catheters or feeding tubes should be cautious about or avoid swimming and resistance training of muscles that might dislodge the catheter.
- with multiple or uncontrolled comorbidities should consult their physicians to consider the most appropriate exercise program.
- with peripheral neuropathy or dizziness should engage in exercise that takes account of their restricted balance and coordination.
Exercise Protocols
Guidelines consistently note that the particular exercise program and when it is initiated should be individualized to the patient's condition and personal preferences.6 A person's level of exercise before diagnosis and treatment must be taken into account. In some cases, increased physical activity prior to surgery or radiation may have beneficial effects on recovery. Inactivity should be avoided.5 The 2012 ACS guidelines recommend that adults should engage in at least 150 minutes per week of moderate intensity activity or 75 minutes per week of vigorous activity, or an equivalent combination of both levels (see Table 2). Moderate activities are those that can be done while talking (e.g., gardening, biking on the flat, walking briskly), while vigorous activities are difficult to do while talking (e.g., hiking uphill, jogging, digging, aerobic dancing).1
For those exercising prior to diagnosis, maintaining exercise levels or returning to earlier levels should be the goal, where appropriate. However, lower intensities or shorter durations may be necessary during treatment. For those who were not exercising before diagnosis, a program of low-intensity exercise that is tailored to the individual should be developed and gradually advanced. Account must be taken of other symptoms and conditions, along with patients' individual interests and enthusiasm for exercise. To develop and monitor individualized exercise programs, people should be referred to a physical therapist or personal trainer with expertise working with cancer survivors.
Conclusion
Growing numbers of studies show that exercise can be beneficial for cancer patients during and after treatment. Most studies have been conducted with breast cancer survivors, with other types of cancer each having relatively few trials. Caution is needed in applying the results from breast cancer to other cancers.6 In general, exercise positively affects cancer survivors' quality of life, fatigue levels, cardiorespiratory fitness, and other outcomes. Improvements with exercise were also noted on some biomarker levels and with symptom management. However, many other exercise outcomes have been inadequately researched to allow evidence-based recommendations. Exercise programs were tolerated well with few adverse events reported.
Recommendation
Evidence increasingly supports encouraging cancer survivors to continue and improve physical activity levels during and after treatment. The evidence is most clear for women with breast cancer, but the few studies with other cancers have had positive results. Exercise recommendations must be tailored to individual patients depending on their activity levels prior to diagnosis and other limitations imposed by their disease or treatment. Guidance should be sought from physical therapists or personal trainers with expertise working with cancer survivors.
Evidence regarding the impact of exercise on secondary cancer prevention and long-term mortality comes primarily from observational trials, but is positive. RCTs in this area are only just beginning, but should provide more clear-cut evidence.
Larger and better designed studies may reveal more specific guidelines for all cancer patients and those with specific types of cancer. Guidelines for specific exercise programs are generally not available as studies have used a wide variety of programs. However, general recommendations from the American Cancer Society are shown in Table 2.2
References
1. Ballard-Barbash R, et al. Physical activity, biomarkers, and disease outcomes in cancer survivors: A systematic review. J Natl Cancer Inst 2012;104:815-840.
2. Rock CL, et al. Nutrition and physical activity guidelines for cancer survivors. CA Cancer J Clin 2012. [Epub ahead of print]
3. Jones LW, et al. Effects of an oncologist's recommendation to exercise on self-reported exercise behavior in newly diagnosed breast cancer survivors: A single-blind, randomized controlled trial. Ann Behav Med 2004;28:105-113.
4. Schmitz KH, et al. Controlled physical activity trials in cancer survivors: A systematic review and meta-analysis. Cancer Epidemiol Biomarkers Prev 2005;14:1588-1595.
5. Schmitz KH, et al. American College of Sports Medicine roundtable on exercise guidelines for cancer survivors. Med Sci Sports Exerc 2010;42:1409-1426.
6. Speck RM, et al. An update of controlled physical activity trials in cancer survivors: A systematic review and meta-analysis. J Cancer Surviv 2010;4:87-100.
7. Ferrer RA, et al. Exercise interventions for cancer survivors: A meta-analysis of quality of life outcomes. Ann Behav Med 2011;41:32-47.
8. Brown JC, et al. Efficacy of exercise interventions in modulating cancer-related fatigue among adult cancer survivors: A meta-analysis. Cancer Epidemiol Biomarkers Prev 2011;20:123-133.
9. Ibrahim EM, Al-Homaidh A. Physical activity and survival after breast cancer diagnosis: Meta-analysis of published studies. Med Oncol 2011;28:753-765.
10. Schmitz K, et al. Weight lifting in women with breast cancer–related lymphedema. N Engl J Med 2009;361:664-673.
As of 2010, about 14 million cancer survivors were living in the United States, with the number projected to increase to 18 million by 2020.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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