Abstract
We aimed to estimate the incremental effects of post-diagnosis recreational aerobic exercise and possible variations in effects on recurrence and mortality to support individualized breast cancer survivorship care plans in clinical settings. Seven databases were searched to identify observational studies that examined the effects of exercise on recurrence, breast cancer-specific mortality, and all-cause mortality (ACM) among female breast cancer survivors. Fully adjusted hazard ratios (HR) and 95% confidence intervals were extracted for comparisons reported in relation to no/minimal exercise (reference). Dose-response relationships between exercise and events were examined using restricted cubic splines. Less than half of participants (44.3%, n = 50,689) met aerobic exercise guidelines for health (≥∼2.5 hours/week). Meeting guidelines was associated with a ∼50% reduction in the HR for ACM, with further reductions up to ∼4.5 hours/week. A ∼25% reduction in the HR for ACM was associated with ∼1 hour/week. The 5-year (unadjusted) ACM rates were 11% for no/minimal exercise, 4% for insufficient exercise, and 3% for meeting exercise guidelines (n = 5 studies). There were limited data for subgroups. Similar patterns were observed for recurrence and breast cancer-specific mortality. Exercise may lower the risk of recurrence and mortality among breast cancer survivors. Though meeting guidelines for health offers the greatest benefits, exercise below guideline-recommended exercise levels is also beneficial.