Exercise and Breast Cancer Recurrence & Survival
Scientists from the University of Southern California published a 2016 review paper summarizing the effects of exercise and diet on breast cancer recurrence. Main take-away points are summarized below:
- 9.8% of women experienced a recurrence of breast cancer on a low-fat (15% total caloric intake) diet vs 12.4% of women who only received written dietary guidelines after 60 months (Women's Healthy Eating and Living Study)
- high animal fat intake is abundant in omega-6 fatty acids which produces eicosanoids. Eicosanoids promote inflammation and blood vessel growth around tumors
- High fruit and vegetable intake may be beneficial because they have chemopreventive compounds such as: carotenoids, polyphenols, and isothiocyanates.
- High fiber intakes may be beneficial because fiber binds estrogen.
- One meta-analysis found an inverse relationship between physical activity and death from all causes and breast cancer related deaths and events.
- recent (less than 12 years prior) pre-diagnosis participation in recreational physical activity decreases all cause and breast cancer related death.
- Nurses' health study demonstrated that exercising at 3-8.9 MET-h/week, 9 - 14.9 MET-h/week, 15-23.9 MET-h/week and 24+ MET-h/week decreased risk of mortality from breast cancer (some by nearly a half) compared to those women who exercised less than 3 MET-h/week.
- In the START trial, the 8-year disease free survival was higher (82.7%) in the exercise group vs those receiving usual care (75.6%). Sub-group analyses suggests that the effect may be even stronger in women who are overweight/obese. (Exercise training was a supervised aerobic or resistance training program).
- Physical activity and exercise may be beneficial because it lowers adiposity and increases skeletal muscle
- 90 women on a 6-month exercise (3 times/week, 65-85% max heart rate aerobic exercise sessions + 10-15 min muscle strengthening exercises) and hypocaloric healthy eating program resulted in moderate weight loss, significant reduction in leptin, total cholesterol, body weight and waist circumference.
- The most consistent finding was that reductions in adiposity accompanied the most beneficial changes in breast cancer outcomes including survival, recurrence risk and biomarkers associated with prognosis.
Currently, the information is drawn mostly from epidemiological data. There needs to be more randomized controlled trials to allow for concrete conclusions. The current evidence suggests exercise and physical activity may be beneficial.
Reference: Dieli-Conwright, C, Lee, K, Kiwata, JL. Reducing the risk of breast cancer recurrence: an evaluation of the effects and mechanisms of diet and exercise. Curr Breast Cancer Rep (2016) 8:139-150