A new study has reported that regular physical activity before a diagnosis of breast cancer improves survival. The study was designed to investigate the influence of recreational physical activity before diagnosis on prognosis. Recreational physical activity (including exercise, sports and hobbies requiring significant exertion) has been reported to be associated with lower risk of breast cancer, but there is little data on whether prediagnostic physical activity influences survival after a diagnosis of breast cancer.

The study included 1,508 women diagnosed in 1996 or 1997 who were enrolled in the Long Island Breast Cancer Study Project. Data concerning lifetime physical activity (which was expressed as metabolic equivalent task hours per week (MET-h/week)) was collected during an in-person interview that took place shortly after diagnosis. A total of 196 study participants died during follow up through year-end 2002.

Women who engaged in an average of nine or more MET-h/week of recreational physical activity from first period to breast cancer diagnosis were found to have a 43% lower risk of death from all causes compared to women who did not exercise. Nine MET-h/week amounts to approximately three hours per week of fast walking. The analysis was adjusted by age and body mass index (BMI). Women who engaged in modest amounts of moderate intensity lifetime recreational physical activity were found to 38% lower risk of death from all causes and 36% lower risk of breast cancer-specific death compared to women who did not engage in moderate physical activity. Among women who were diagnosed with breast cancer after menopause, recreational physical activity that took place after menopause was associated with a 39% reduction in overall mortality. However, no reduction in mortality was found for postmenopausal breast cancer patients due to recreational physical activity that took place before menopause. The authors conclude that recreational physical activity prior to breast cancer diagnosis improves survival.

Heavy exercise is not recommended during chemotherapy or radiation treatment

Other studies have also reported that moderate physical activity reduces the risk of breast cancer and may improve survival. Exercise has been shown to reduce inflammation and change estradiol and sex hormone binding globulin levels in ways that are consistent with lower risk of postmenopausal breast cancer. Exercise may also affect regulation of tumor suppressor genes in ways that have favorable influence on survival outcomes. However, note that heavy exercise is not recommended during radiation treatment or chemotherapy because it may interfere with the effectiveness of treatment.