Physical activity before, during, and after chemotherapy for high-risk breast cancer: Relationships with survival

Abstract

Background: Although physical activity has been consistently associated with reduced breast cancer mortality, evidence is largely based on data collected at one occasion.We examined how pre- and postdiagnosis physical activity was associated with survival outcomes in high-risk breast cancer patients. Methods: Included were 1340 patients enrolled in the Diet, Exercise, Lifestyle and Cancer Prognosis (DELCaP) Study, a prospective study of lifestyle and prognosis ancillary to a SWOG clinical trial (S0221). Activity before diagnosis, during treatment, and at 1- and 2-year intervals after enrollment was collected. Patients were categorized according to the Physical Activity Guidelines for Americans as meeting the minimum guidelines (yes/no) and incrementally as inactive, low active, moderately active (meeting the guidelines), or high active. Results: In joint-exposure analyses, patients meeting the guidelines before and 1 year after diagnosis experienced statistically significant reductions in hazards of recurrence (hazard ratio [HR]=0.59, 95% confidence interval [CI] = 0.42 to 0.82) and mortality (HR=0.51, 95% CI = 0.34-0.77); associations were stronger at 2-year follow-up for recurrence (HR=0.45, 95% CI = 0.31 to 0.65) and mortality (HR=0.32, 95% CI = 0.19 to 0.52). In time-dependent analyses, factoring in activity from all time points, we observed striking associations with mortality for low- (HR = 0.41, 95% CI = 0.24 to 0.68), moderate- (HR = 0.42, 95% CI = 0.23 to 0.76), and high-active patients (HR=0.31, 95% CI = 0.18 to 0.53). Conclusions: Meeting the minimum guidelines for physical activity both before diagnosis and after treatment appears to be associated with statistically significantly reduced hazards of recurrence and mortality among breast cancer patients. When considering activity from all time points, including during treatment, lower volumes of regular activity were associated with similar overall survival advantages as meeting and exceeding the guidelines.