Physical activity in breast cancer survivors: A systematic review and meta-analysis on overall and breast cancer survival

Aim: To further quantify the association between physical activity (PA) after breast cancer diagnosis and all-cause mortality, breast cancer mortality and/or breast cancer recurrence. Methods and results: PubMed was searched until November 2017 for observational studies investigating any type of PA in association with total mortality, breast cancer mortality and/or breast cancer recurrence among women with breast cancer diagnosis. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using random-effects models for highest versus lowest categories of PA. Ten studies were included in the meta-analysis. During an average follow-up ranging from 3.5 to 12.7 years there were 23,041 breast cancer survivors, 2,522 deaths from all causes, 841 deaths from breast cancer and 1,398 recurrences/remissions. Compared to women in the lowest recreational PA level (lowest quintile/quartile), women in the highest level had a lower risk of all-cause mortality (HR = 0.58, 95% CIs: 0.45 -0.75; 8 studies), of death from breast cancer (HR = 0.60, 95% CIs 0.36-0.99; 5 studies) and a lower, albeit non-significant, risk of recurrence (HR = 0.79, 95% CIs 0.60-1.05; 5 studies). There was evidence of heterogeneity between the studies evaluating recreational PA and total mortality (I-2 = 52.4%) and even higher for breast cancer mortality (I-2 = 77.7%) or recurrence (I-2 = 66.4%). Conclusion: Highest recreational PA after breast cancer diagnosis was associated with lower all-cause and breast cancer mortality. This finding probably reflects the favorable impact of PA on cardiovascular mortality, and a possible favorable role on breast cancer survival, though reverse causation cannot be excluded. (C) 2019 Elsevier Ltd. All rights reserved.