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Breast Cancer
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Weight Management and Physical Activity for Breast Cancer Prevention and Control
Abstract
Observational evidence has consistently linked excess adiposity and inactivity to increased breast cancer risk and to poor outcomes in individuals diagnosed with early-stage, potentially curable breast cancer. There is less information from clinical trials testing the effect of weight management or physical activity interventions on breast cancer risk or outcomes, but a number of ongoing trials will test the impact of weight loss and other lifestyle changes after cancer diagnosis on the risk of breast cancer recurrence. Lifestyle changes have additional benefits beyond their potential to decrease primary or secondary breast cancer risk, including improvements in metabolic parameters, reduction in the risk of comorbidities such as diabetes and heart disease, improvement of physical functioning, and mitigation of side effects of cancer therapy. Despite these myriad benefits, implementation of lifestyle interventions in at-risk and survivor populations has been limited to date. This article reviews the evidence linking lifestyle factors to breast cancer risk and outcomes, discusses completed and ongoing randomized trials testing the impact of lifestyle change in primary and secondary breast cancer prevention, and reviews efforts to implement and disseminate lifestyle interventions in at-risk and breast cancer survivor populations.
Weight management across the lifespan is important to reduce the risk of breast cancer and other chronic conditions that can increase breast cancer risk and poor outcomes.
Physical activity is associated with risk of breast cancer, independent of body mass index, but is also partially attributed to its favorable effects on body weight and composition.
Observational evidence suggests that obesity and inactivity are linked to an increased risk of breast cancer recurrence and mortality; ongoing trials will evaluate whether lifestyle change after breast cancer diagnosis will improve outcomes.
Physical activity after breast cancer diagnosis has been shown to reduce fatigue and other side effects related to cancer treatment and to improve quality of life and fitness in survivors of breast cancer.
Free resources to encourage a physically active lifestyle for the prevention of breast cancer and other chronic conditions may be found online (https://health.gov/paguidelines/moveyourway/toolkit/); the updated guide for physical activity among cancer survivors will be released by the American College of Sports Medicine in 2019.
Growing evidence suggests a role for weight management and increased physical activity in breast cancer prevention and control. Numerous observational studies demonstrate that postmenopausal women with obesity are at increased risk of developing breast cancer,1 and obesity is linked to increased risk of breast cancer recurrence and mortality in both pre- and postmenopausal women.2 Similarly, observational evidence suggests that inactivity, independent of its contribution to excess adiposity, is a risk factor for breast cancer incidence3-5 and mortality.6 Despite the strong and consistent evidence linking obesity and inactivity to breast cancer risk and outcomes, less is known about the impact of weight loss or physical activity interventions in lowering breast cancer risk or in improving outcomes in individuals diagnosed with early-stage, potentially curable breast cancer. Additionally, despite the evidence linking a healthy lifestyle to lower breast cancer risk and better breast cancer outcomes, obesity and inactivity are prevalent, both in women at risk for developing breast cancer and in breast cancer survivors.7,8 Strategies are needed to disseminate weight management and physical activity programs to these populations to optimize breast cancer outcomes. This article reviews the evidence linking lifestyle factors to breast cancer risk and outcomes, discusses completed and ongoing randomized trials testing the impact of lifestyle change in primary and secondary breast cancer prevention, and reviews efforts to implement and disseminate lifestyle interventions in at-risk and breast cancer survivor populations.
There is a large body of evidence demonstrating that overweight and obesity, characterized by body mass index (BMI), are associated with an increased risk of postmenopausal breast cancer. In contrast, obesity has not been associated with increased risk of premenopausal breast cancer.1,4,9,10 In fact, higher BMI has been associated with a reduced risk of premenopausal breast cancer. Given that breast cancer is most frequently diagnosed among postmenopausal women,11 this section will largely focus on primary prevention of postmenopausal breast cancer. However, lifestyle strategies that impact adiposity and have independent effects are also applicable to premenopausal women because healthy body weight, diet, and physical activity are protective against the majority of noncommunicable diseases, such as diabetes and cardiovascular disease.
Greater than 70% of Americans are overweight or obese.12 BMI categories are normal weight (< 25 kg/m2), overweight (≥ 25 to < 30 kg/m2), and obese (≥ 30 kg/m2). Obesity is associated with breast cancer risk reduction among premenopausal women,1,4 but overweight or obesity is associated with 1.5 to 2 times increased risk of postmenopausal breast cancer, respectively.1 Estrogen receptor–positive (ER+) and progesterone receptor–positive (PR+) breast cancers, specifically, as well as risks of advanced disease and death have been elevated among postmenopausal women with excess adiposity.13
Early adult,14-17 midlife, and menopausal weight gain16-19 have all been associated with increased risk of postmenopausal breast cancer in longitudinal and case-control analyses, with minimal disagreement.20 It has been estimated that every 5 kg of weight gain above the lowest adult weight is associated with a 4% to 8% increase in postmenopausal breast cancer risk.21,22 However, this risk appears to be limited to or stronger among individuals who do not use hormone therapy (HT).14,15,23-27 Higher risks associated with weight gain among patients who do not use HT may be particularly relevant for advanced disease.16 In addition, weight gain has been more strongly associated with ER+ and PR+ than for ER− and PR− tumors,28 which may be related to greater central adiposity among patients who do not use HT.22
Conversely, weight loss has been associated with a reduced risk of breast cancer in longitudinal studies and case-control studies,14,15,17,21,29 although the results of one study limited to overweight and obese women were nonsignificant.30 However, the timing of weight loss in the life cycle may be important. For example, weight loss among women whose highest weight occurred after age 45 was not associated with breast cancer risk (odds ratio [OR], 1.00; 95% CI, 0.95–1.05) but was associated with a reduced risk of postmenopausal breast cancer if the highest weight was before age 45 (OR, 0.90; CI, 0.84–0.98, per 5 kg).21
Weight fluctuations, also termed weight cycling, occur among overweight and obese women when maintenance of intentional weight loss cannot be achieved. Although one small case-control study demonstrated an increased risk of postmenopausal breast cancer with weight fluctuations,31 the majority of large national longitudinal cohort studies and case-control studies have not.21,32-34 Based on these observational data, it appears that weight cycling is not associated with an increased risk of breast cancer.
Importantly, there may be racial/ethnic differences in the associations between weight changes and breast cancer risk. There is some suggestion that increased risk of breast cancer among Hispanic women with weight gain in early life may be independent of menopausal status,23 which differs from non-Hispanic women. Among Asian women, high BMI combined with recent weight gain (≥ 4.5 kg, approximately) in midlife poses the greatest risk,19,35 whereas recent weight loss may be associated with reduced breast cancer risk.19 Further prospective studies are needed to confirm these racial/ethnic differences.
BMI is a proxy for body fat across populations and is not a sensitive measure for adiposity or lean mass within individuals. Specific tissue volumes and patterns of deposition are not reflected in BMI, which relies on total mass and height. Deleterious changes in body composition compartments (increased fat and decreased lean mass) and deposition patterns (preferential abdominal fat deposition) with aging can be masked by stable BMI. The insufficient precision of BMI for adipose estimation with aging likely plays a role in the differential pre- versus postmenopausal relation between breast cancer and obesity. Furthermore, because metabolic dysfunction, inflammation, and production of postmenopausal estrogen are associated with increased adiposity, particularly visceral adipose tissue, it is important to consider more direct measures of body composition such as dual-energy x-ray absorptiometry.
Chronic low-grade inflammation and metabolic dysfunction are believed to be intermediate biomarkers linking obesity to postmenopausal breast cancer. Indeed, metabolic syndrome36 and type 2 diabetes accompanied by obesity have been established as notable risk factors for postmenopausal breast cancer.37,38 However, type 2 diabetes alone is associated with increased risk of breast cancer, independent of BMI.39
Although it is difficult to study weight- or fat-specific loss as a primary prevention intervention for the reduction of breast cancer risk because of the length of follow-up required, reductions in body weight among overweight and obese individuals have been shown to reduce chronic low-grade inflammation and to partially or completely resolve metabolic disturbances, which supports reduced risk of other chronic conditions and potentially breast cancer risks. Therefore, both adiposity and metabolic dysfunction, which can be favorably altered by diet and activity with and without weight change, are relevant targets for breast cancer risk reduction.36
Mammographic screening is recommended by most leading organizations for women with average risk, with some variability in age to initiate/terminate screening.40,41 Importantly, it has been suggested that obesity may interfere with screening uptake and effectiveness.42-44 Discomfort discussing weight issues, appointment cancelations, technical limits regarding body size and breast tissue mobility, and gown and imaging window fit have been cited as potential barriers to screening effectiveness.42 Additionally, high mammographic density is positively associated with breast cancer. Although BMI is inversely associated with breast density, adult weight gain has been associated with the proportion of dense tissue in the breast.45 Keeping these issues in mind when discussing weight management and screening recommendations with patients is prudent.
Physical activity is an important component of weight management. Higher levels of physical activity have also been associated with a reduced risk of breast cancer.3-5 Achieving the World Health Organization’s recommendations for leisure time physical activity (≥ 10 MET-hours/week) is associated with a significantly lower risk of breast cancer.46 It has been debated whether the reduction of the risk of breast cancer with physical activity is attributable, in part, to its positive effects on weight and body composition.47-49 Some have shown that the relationship between physical activity and breast cancer is independent of BMI, ER status, weight gain, and HT.5,47,49,50 There is also the suggestion that vigorous activity may be required for risk reduction,50 whereas some have shown risk reductions with walking49 and household activities for both pre- and postmenopausal breast cancer.51 Most impressively, physical activity is associated with decreased breast cancer risk independent of smoking status5 and is associated with a significantly delayed onset of breast cancer among BRCA carriers.52 Although the exact dose and type of activity required to reduce breast cancer risk is yet to be determined, it is clear that physical activity is associated with a reduced risk of breast cancer.
Proposed mechanisms of action for physical activity reductions in breast cancer risk include favorable reductions in estrogen availability, inflammation, and metabolic dysfunction, in addition to improved body composition.53 More research is needed to fully understand the mechanisms by which physical activity could reduce breast cancer risk. However, implementing a physically active lifestyle has little downside, with much to gain. Most U.S. adults do not meet the recommended levels of physical activity.54 Therefore, increasing physical activity should be considered an important strategy for breast cancer risk reduction, regardless of weight status and other lifestyle factors (Table 1). Recently updated Physical Activity Guidelines for Americans are available (https://health.gov/paguidelines/second-edition/).55,56
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Weight management and physical activity are recommended for cancer prevention by leading U.S. and international organizations, alongside other preventive behaviors3,4 to address the multifaceted nature of prevention (Table 2). Women meeting at least five of the World Cancer Research Fund/American Institute for Cancer Research recommendations had a 60% lower risk of breast cancer (hazard ratio [HR], 0.40; 95% CI, 0.25–0.65), with further reduction in breast cancer risk with each additional recommendation met (HR, 0.89; 95% CI, 0.84–0.95).57 A recent systematic review demonstrated alignment with these findings, and adherence to cancer prevention guidelines was associated with a 13% to 60% reduction in breast cancer risk.58
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In addition to data linking obesity, inactivity, and, to some extent, dietary quality to breast cancer risk, observational studies also suggest that these factors may also impact outcomes in women diagnosed with early-stage breast cancer. The relationship between body weight at the time of breast cancer diagnosis and the risk of breast cancer recurrence and mortality has been evaluated in more than 100 reports over the last 40 years.2,59,60 A 2014 meta-analysis including 82 studies and encompassing 213,075 women with early-stage breast cancer reported a 35% increase in breast cancer–related mortality and a 41% increase in overall mortality in women who were obese at the time of breast cancer diagnosis compared with women who were of normal weight. Interestingly, the relationship between obesity and increased risk of mortality did not vary by menopausal status, with obese premenopausal women having a 75% increased risk of mortality after breast cancer diagnosis compared with normal-weight premenopausal women (relative risk [RR], 1.75; 95% CI, 1.26–2.41) and obese postmenopausal women having a 34% increased risk of mortality after cancer diagnosis compared with obese postmenopausal women (RR, 1.34; 95% CI, 1.18–1.53).2
In addition to the relationship between obesity and increased risk of breast cancer and overall mortality, obesity has also been shown to be associated with an increased risk of second primary malignancies in breast cancer survivors. A review and meta-analysis by the World Cancer Research Fund of eight studies evaluating the relationship between BMI and risk of contralateral breast cancer in breast cancer survivors found that for each 5-kg/m2 increase in BMI, there was a 13% increase in the risk of contralateral breast cancer (summary RR, 1.13; 95% CI, 1.06–1.21).61 When comparing the highest to lower BMI categories, the summary RR for contralateral breast cancer was 1.30 (95% CI, 1.14–1.48). Similarly, in four studies that evaluated the relationship between BMI and risk of endometrial cancer among breast cancer survivors, survivors with the highest BMI versus the lowest had a 94% increase in the risk of endometrial cancer (summary RR, 1.94; 95% CI, 1.45–2.59).
Although the literature is more limited, observational studies have also evaluated the relationship between physical activity patterns after breast cancer diagnosis and cancer recurrence and mortality. A recent meta-analysis of 16 cohort studies, encompassing 42,602 patients, demonstrated that breast cancer survivors who engaged in the highest levels of physical activity after cancer diagnosis had a 29% lower risk of breast cancer–specific mortality (RR, 0.71; 95% CI, 0.58–0.87, p < .01) and a 43% lower risk of all-cause mortality (RR, 0.57; 95% CI, 0.45–0.72, p < .01) compared with inactive breast cancer survivors.6
Finally, numerous efforts have been made to evaluate the relationship between breast cancer outcomes and dietary patterns and intake of specific nutrients and foods. A thorough review of this work is beyond the scope of this article, but was summarized in a recent review by the World Cancer Research Fund.61 Although individual studies have shown associations between various dietary elements and mortality in breast cancer survivors, data have largely been inconsistent.
Despite the consistent evidence linking lifestyle factors to breast cancer prognosis, there are relatively few studies that have evaluated the effect of lifestyle change—weight loss, increased physical activity, or dietary change—after breast cancer diagnosis on the risk of cancer recurrence or mortality. Two trials, both initiated almost 3 decades ago, evaluated the impact of dietary change on breast cancer recurrence and mortality. Both studies focused on reduction in dietary fat. The Women’s Intervention Nutrition Study randomly assigned 2,437 women with stage I to III breast cancer whose diets included at least 20% of daily calories from fat to a low-fat dietary intervention, with a target goal of reducing fat to ≤ 15% of daily calories, or to a usual-care control group.62 Intervention participants decreased dietary fat intake and body weight compared with controls. After a median follow-up of 5.6 years and 227 relapse events, disease-free survival was significantly better in intervention participants compared with controls (HR, 0.76; 95% CI, 0.60–0.98). With further follow-up, these findings lost statistical significance, but an exploratory subgroup analysis demonstrated a significant survival benefit of the intervention for patients with ER− breast cancer (HR, 0.41; p = .003).63 The Women’s Healthy Eating and Living study had a similar design, randomly assigning 3,088 women with stage I to III breast cancer to a usual-care control group or to a dietary intervention focused on increasing intake of fruits, vegetables, and fiber and lowering fat intake.64 Patients were eligible regardless of baseline diet. Intervention participants significantly increased intake of fruits and vegetables and decreased the percentage of dietary calories from fat, but they did not experience weight loss. After a median follow-up of 7.3 years and 518 relapse events, there was no difference in recurrence rates in the diet and control groups (16.7% vs. 16.9%; p = .63).
More recent randomized trials are evaluating the impact of interventions including both physical activity and dietary components on breast cancer recurrence and survival. The SUCCESS-C trial was a phase III randomized trial with a two-by-two factorial design, first randomly assigning women with stage II to III breast cancer to one of two chemotherapy regimens and subsequently randomly assigning women with a BMI between 24 and 40 kg/m2 to a telephone-based weight loss intervention or usual-care control group.65 Preliminary trial results were presented at the San Antonio Breast Cancer Symposium in December 2018.66 A total of 2,292 participants in the SUCCESS-C trial met the BMI requirements and were randomly assigned to the weight loss intervention group versus the control group. The weight loss intervention was composed of a calorie-restricted, low-fat diet combined with increased physical activity and was delivered through 19 phone calls over the duration of the 2-year intervention period. Baseline BMI of study participants was approximately 28 kg/m2. Over the 2-year intervention period, patients randomly assigned to the weight loss intervention lost an average of 1 kg versus a 0.95-kg weight gain in controls (p < .001). More than 50% of the patients in the weight loss intervention group dropped out of the program, compared with 20% of controls. There were no differences in disease-free or overall survival in the weight loss intervention versus control groups in intention-to-treat analyses. Exploratory unplanned analyses suggest that participants who completed the 2-year intervention period had better disease-free and overall survival than patients who dropped out (p < .001). Among individuals who completed the study, there was a lower rate of cancer recurrence and mortality in individuals assigned to the weight loss arm; however, the differential drop-out rates and differences in participants who completed the weight-loss intervention versus those who dropped out make interpretation of these findings difficult.
Two additional ongoing trials will test the effect of diet and exercise interventions on breast cancer recurrence and mortality. The DIANA-5 study is a randomized trial testing the impact of a Mediterranean lifestyle intervention on breast cancer recurrence among 1,214 Italian women with stage I to III breast cancer.67 Participants were randomly assigned to a lifestyle intervention focused on exercise and consumption of a Mediterranean, macrobiotic diet or to a usual-care comparison group. Patient recruitment was completed in 2010 and follow-up is ongoing. The Breast Cancer Weight Loss (BWEL) study is a National Cancer Institute–funded phase III randomized trial evaluating the effect of a weight loss program on cancer recurrence among 3,136 overweight and obese women with stage II to III breast cancer in the United States and Canada.68 Study participants are randomly assigned to a 2-year telephone-based weight loss program or to a control group. All participants receive a health education program consisting of evidence-based materials supporting a healthy lifestyle. The study opened to enrollment in August 2016 and is currently accruing participants from more than 1,100 oncology practices across North America. As of March 1, 2019, 1,900 women had been enrolled. Study results are anticipated in approximately 2024.
Although relatively few large-scale randomized trials have tested the effect of lifestyle interventions on breast cancer recurrence and survival, many smaller interventional trials have evaluated the impact of exercise and weight loss interventions on a diverse array of outcomes for breast cancer survivors. Meta-analyses have demonstrated consistent evidence that exercise interventions lead to improvements in cardiorespiratory fitness69 and physical functioning,70 as well as reductions in fatigue.71 More limited evidence also suggests that exercise interventions can reduce anxiety72 and depression73 and lead to improvements in quality of life.70 Studies have also shown that structured exercise interventions can reduce the risk of lymphedema after axillary surgery and can also reduce the frequency of exacerbations in women who have already developed lymphedema.74 Trials have also demonstrated that exercise and weight loss interventions can lead to reductions in fasting insulin and improvements in other metabolic and inflammatory biomarkers,75,76 providing insight into the biologic mechanisms through which these factors could impact breast cancer risk and outcomes as well as reduce comorbidities and improve overall health.
Based on the evidence presented above, the American Cancer Society has developed guidelines for nutrition and physical activity for cancer survivors (Fig. 1).77 The National Comprehensive Cancer Network also includes nutrition, weight management, and physical activity as part of its survivorship recommendations.78 However, incorporating these components into survivorship care presents challenges, and information on research and best practices is not readily available. Providers report multiple barriers to addressing these issues in survivorship care, including lack of knowledge and training in this area, uncertainty about when in the cancer continuum to introduce it, lack of support from hospital administration, and issues of time and patient flow.79,80 Supporting cancer survivors in physical activity and weight management behavior can take a number of different forms with varying intensity.
FIGURE 1. American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Survivors
Adapted from Rock et al.77
At a minimum, oncology practices should provide evidence-based information to breast cancer survivors about physical activity, nutrition, and weight management. Many survivors will have questions about whether it is appropriate for them to be physically active. Additionally, survivors often are concerned that they will lose weight after diagnosis, but weight gain is common among breast cancer survivors, and survivors should be taking steps to avoid weight gain. A lack of education, or worse, misinformation obtained from unqualified sources on the internet or within the community may confuse survivors about the optimal course to take with regard to physical activity and weight management. Survivorship care providers can serve as a credible and trusted information source. Provision of educational materials that are clear and readable, attractive, and available in appropriate language by an oncology practice can ensure that survivors have the basic information about health behavior recommendations. Practices that have patient education resources can work with these resources to develop patient materials, whether they be print materials or digital. For practices that do not have an in-house patient education department, resources such as the American Society of Clinical Oncology booklet Managing Your Weight After a Cancer Diagnosis: A Guide for Patients and Families (www.cancer.net/sites/cancer.net/files/weight_after_cancer_diagnosis.pdf), the American Cancer Society website (www.cancer.org/treatment/survivorship-during-and-after-treatment/staying-active.html), or the National Comprehensive Cancer Network website (www.nccn.org/patients/resources/life_after_cancer/nutrition.aspx and www.nccn.org/patients/resources/life_after_cancer/exercise.aspx) may be helpful.
Patients with cancer and survivors express a strong preference to receive information about physical activity, diet, and weight management from their oncology providers,81 and studies indicate that such discussions can be influential82,83 and are associated with increased physical activity among cancer survivors.84,85 Providers may not have time to provide extensive counseling about physical activity, nutrition, and weight management but can help by raising the topic. Doing so establishes the importance of these behaviors after cancer diagnosis, and providers can reassure patients who might be uncertain about the safety or appropriateness of exercise or weight loss after treatment. Furthermore, providers can identify any precautions that are necessary or additional testing that might be warranted for the patients. One model for encouraging provider counseling borrowed from the smoking cessation field is the “5As” model (Ask, Advise, Assess, Assist, Arrange),86 which has been shown to be a successful approach to motivate smokers to quit and connect them with cessation interventions. With some modification, this model can be adapted to counseling cancer survivors about weight and physical activity. Vallis et al87 suggest adding “agree” to the 5As when counseling patients about obesity. To assess patient readiness and avoid having patients feel stigmatized about their weight, it is appropriate to first ask patients whether they are willing to talk about their weight. This step should include assessment of current activity, weight status, physical limitations, and questions about the patient’s goals and preferred activities/modes of seeking help.
Once a survivor agrees to work toward weight management and/or a more physically active lifestyle, some assessment of the survivor’s health status is needed. Survivors’ comorbid health conditions and cancer sequelae can affect the medical clearance needed and type of exercise or weight loss setting that is most appropriate. For example, survivors who have lymphedema should have this condition evaluated and treated by a lymphedema specialist before starting an exercise program that involves upper body exercise. In addition, they should be referred initially to a program supervised by an exercise professional with expertise in this area, because upper body resistance training should start with low resistance and proceed slowly to prevent injury that could exacerbate lymphedema. For patients with chronic disease, the American College of Sports Medicine (ACSM) recommendations88 for preparticipation health screening can be followed, with adaptation as needed for cancer-related conditions. The ACSM recommends medical clearance for (1) people who are not currently exercising and have known cardiovascular, metabolic, or renal disease or any signs and symptoms; or (2) people who are currently exercising and have signs or symptoms of cardiovascular, metabolic, or renal disease. For patients who are currently exercising and have known cardiovascular, metabolic, or renal disease, the ACSM recommends medical clearance only if the patient wants to begin vigorous intensity exercise. The clearance/evaluation needed should also be tailored to the type of exercise or physical activity the participant is willing to do. The majority of cancer survivors express that walking is their preferred form of physical activity.89 Walking is a relatively safe form of exercise that can be done by the majority of survivors and is unlikely to require extensive medical clearance or a supervised setting.
Programs to help cancer survivors address weight or physical activity must reflect the diversity of their needs, interests, goals, preferences, and resources. Programs can be delivered as supervised, monitored, or unsupervised, each suggesting different roles for professionals. Although some survivors may be able to proceed with exercise or weight management independently, others may experience barriers that make lifestyle change challenging or even unsafe in unsupervised settings and thus must be part of a structured cancer rehabilitation program before proceeding with home- or community-based programs.90 Survivors also differ in their motivation for pursuing lifestyle programming. Some seek health promotion that targets the prevention of future health problems, whereas others must remediate impairments and activity limitations through medical rehabilitation. Mobile health intervention strategies (e.g., mobile apps, wearables) may be useful across the range of programs, either to provide information and self-monitoring support to survivors in supervised programs, or as free-standing interventions for survivors who are interested in a self-directed program.91 Optimal design of such interventions to maximize engagement and effectiveness is a critical research need.92 Regardless of program type or delivery characteristics, all programs must be evidence based, with demonstrated efficacy, effectiveness, and safety.
One notable community-based exercise program tailored to the needs of cancer survivors is the LIVESTRONG at the YMCA program. This 12-week lifestyle change program has been shown to increase physical activity and improve quality of life and fitness.93 It is currently offered in 735 communities, making it the most widely available cancer-specific lifestyle program. Cancer survivors who prefer individual interventions may want to seek out a personal trainer with expertise in working with cancer survivors. The ACSM has a Cancer Exercise Trainer certification program. Certified trainers can be identified through the “Find a Pro” feature on the ACSM website (https://certification2.acsm.org/profinder?_ga=2.139239987.1600007473.1525799292-1759941655.1523997371).
The answer to this question largely depends on the health needs and functional limitations of the individual survivor, the survivor’s risk level of the activity, and his or her comfort level. A cancer-specific program that provides appropriate guidance and supervision to minimize risk is appropriate for survivors who experience or are at risk for substantial treatment side effects (e.g., survivors at risk for lymphedema, undernutrition, or health problems exacerbated by prevalent comorbidities). However, some survivors, even those with relatively few cancer sequelae, may lack self-efficacy for lifestyle behavior change after cancer.94,95 These individuals may be more comfortable with a program that can address their specific needs and concerns, as well as reinforce the survivor-specific benefits of improved lifestyle factors.96
Clearly, cancer survivors need wider availability of a range of programs. Medically based programs may be limited to people receiving care at major centers, and access is also limited by cost, availability of transportation, and time away from work that may be required. Program standards are needed for community programs to assure survivors and providers that offered services are safe and evidence based. To better connect survivors with appropriate programs, we must highlight a variety of evidence-based programs on websites of cancer centers and of national nonprofit organizations, and ideally in a national registry. Additional research and program evaluation is needed to further bolster program safety and effectiveness, identify which programs are effective for whom, and test models of program delivery that are efficient, effective, and sustainable.
Growing evidence supports the role of weight management and physical activity in breast cancer prevention and control. Excess adiposity and adult weight gain are associated with both increased risk of postmenopausal breast cancer and with increased risk of breast cancer–related and overall mortality in both pre- and postmenopausal women. Conversely, increased physical activity is associated with both lower breast cancer risk and better outcomes in individuals with early-stage disease. Trials evaluating the impact of lifestyle change after cancer diagnosis on recurrence and mortality among women with early-stage breast cancer are currently ongoing, but existing evidence suggests important benefits of lifestyle interventions after cancer diagnosis. Additional research is needed to establish best practices for the implementation of these programs in survivor populations. Given that nearly three-quarters of adults, as well as breast cancer survivors, in the United States are overweight or obese and are insufficiently active, physical activity and weight management efforts are critical to both reduce breast cancer risk and improve outcomes.
Disclosures provided by the authors and data availability statement (if applicable) are available with this article at DOI https://doi.org/10.1200/EDBK_237423.
The following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO's conflict of interest policy, please refer to www.asco.org/rwc.
Travel, Accommodations, Expenses: Shawnee Mission Health Shawnee Mission Health
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