Impact of Lifestyle Factors on Prognosis Among Breast Cancer Survivors in the USA

Rachel E Ellsworth; Allyson L Valente; Craig D Shriver; Barry Bittman; Darrell L Ellsworth


Expert Rev Pharmacoeconomics Outcomes Res. 2012;12(4):451-464. 

In This Article

Physical Activity & Breast Cancer Prognosis

Large cohort studies consistently demonstrate the importance of physical activity on breast cancer mortality and survival (Table 2). Data from the NHS from 2987 women with stage I–III breast cancer showed that any amount of exercise above three metabolic equivalent task (MET) hours per week (the equivalent of walking at a moderate pace of 2–3 miles per hour for 1 h) had a beneficial effect on survival. In patients with the highest activity, breast cancer recurrence and mortality were 26–40% lower than in women with the lowest activity.[62] In the LACE study, higher self-reported physical activity was significantly associated with lower all-cause mortality in 1970 breast cancer survivors.[63] The CWLS, which examined 4482 women diagnosed with breast cancer between 1988 and 2001, suggested that women who engaged in >2.8 MET hours per week had a 35–49% lower risk of breast cancer-related mortality compared with those who were physically inactive, even after adjusting for confounding factors such as disease stage, treatment modality, BMI and age at diagnosis. Moderate activity appeared to provide the greatest benefit, with vigorous activity providing no additional survival advantage.[64] Likewise, women in the HEAL study who were physically active in the year immediately prior to diagnosis or 2 years postdiagnosis showed significantly lower breast cancer mortality than women who were inactive. Women who decreased their activity after diagnosis had a fourfold increase in mortality, while those who increased their activity had a 45% lower risk of death.[65] Among 4643 postmenopausal women in the WHI study, those who engaged in ≥9 MET hours/week of recreational physical activity before diagnosis had lower all-cause mortality compared to women who were inactive. Importantly, women with ≥9 MET hours/week after diagnosis had lower all-cause and breast cancer mortality, even if they were inactive before diagnosis.[66] Results from the WHEL trial showed that among 2361 breast cancer survivors, women who were most active following treatment had a 53% lower mortality risk compared with the least active women.[67]

Recent meta-analyses, which include many of the prospective cohort studies mentioned above, support the positive role of physical activity on breast cancer outcomes. One meta-analysis evaluating 12,108 patients with breast cancer from six studies found that physical activity before diagnosis was associated with an 18% reduction in all-cause mortality, while physical activity after diagnosis reduced breast cancer mortality by 34%, all-cause mortality by 41% and disease recurrence by 24%.[68] In a second analysis of 13,302 women from four studies, the After Breast Cancer Pooling Project observed that engaging in ≥10 MET hours/week of moderate physical activity was associated with a 27% reduction in all-cause mortality and a 25% reduction in breast cancer-related mortality compared with women engaging in <10 MET hours/week.[69]

Research has shown that in addition to the beneficial effects on mortality and survival, physical activity can lower the risk of developing breast cancer.[70–72] Nevertheless, fewer than 50% of patients undergoing treatment, especially chemotherapy, engage in regular physical activity. As demonstrated in the HEAL study, physical activity decreased by approximately 2 h per week after diagnosis compared with activity levels 1 year before diagnosis.[73] Similarly, Belgian women (n = 267) with invasive breast cancer showed a significant decrease in activity during the first month postdiagnosis, and did not resume normal activity levels during the first year.[74]

Most research to date strongly supports the link between physical activity and improved breast cancer prognosis, as well as a reduction in comorbid conditions such as cardiovascular disease and diabetes. Despite these findings, several issues, such as the optimal form of physical activity, the frequency and duration of activity and an individualized versus a standardized activity regimen, remain unresolved. Most studies indicate that moderate-intensity aerobic exercise provides the most benefit in terms of prognosis, prompting organizations such as the US Department of Health and Human Services, ACS and American College of Sports Medicine to recommend at least 150 min of moderate, or 75 min of intense, aerobic exercise per week, as well as strength training at least twice a week to achieve significant health benefits.[75,203,204] In addition, a personalized activity plan may be more effective than a standardized regimen because an individual plan can be customized for different time periods from prediagnosis through cancer treatment based on individual needs and abilities. Perhaps the most important factor affecting breast cancer survivors is long-term compliance with any exercise plan. In order to derive maximum benefit, activity must become integrated into each patient's daily routine to ultimately be successful.

Strength Training & Lymphedema

Lymphedema results from the accumulation of excess fluid in the lymphatic system after breast cancer surgery and/or radiation therapy, and may cause pain, swelling, numbness, stiffness and fatigue in the affected arm.[76] Approximately 30% of breast cancer survivors suffer from lymphedema, which can adversely affect physical and psychosocial wellbeing.[77] Obese patients (BMI > 30) in particular are 3.6-times more likely to develop lymphedema compared with women with a BMI <30, thus the National Lymphedema Network encourages obese women to receive nutrition and weight reduction education.[205]

Risk factors for lymphedema include the number of axillary lymph nodes surgically removed or damaged by radiation, obesity at diagnosis or weight gain after treatment, or activities that irritate or inflame the lymphatic system. In the past, a number of breast cancer advocacy groups such as the ACS, Komen for the Cure, and the National Lymphedema Network recommended limited use of the affected arm to decrease risk of lymphedema. Although these recommendations were designed as risk-reduction strategies, limited use may make daily activities more challenging and actually increase risk of injury.[78]

Two recent randomized clinical trials challenged the widespread recommendation that lymphedema patients should limit use of the affected/at-risk arm. The PAL trial randomized 141 breast cancer survivors with lymphedema and 154 survivors at risk for lymphedema to either a nonexercising control group or to an intervention group who performed progressive weight training twice a week for 1 year. The intervention group showed greater improvements in self-reported symptoms and greater overall strength.[79] Importantly, progressive weight lifting did not exacerbate lymphedema. In at-risk patients who had five or more lymph nodes surgically removed, weight training had a noticeable effect on outcome – 22% of controls developed symptoms of lymphedema compared with only 7% of patients who participated in weight training.[80] Observations that progressive strength training is actually beneficial to patients have revolutionized current concepts of lymphedema treatment and altered current guidelines.[206]