Effects of Diet and Exercise induced Weight Loss on Biomarkers of Inflammation in Breast Cancer Survivors: A Systematic Review and Meta-Analysis.

Background: Adiponectin, leptin, and pro- and anti-inflammatory cytokines are implicated in breast cancer risk and recurrence. Weight loss, via the dynamic interplay of energy balance through exercise and/or caloric restriction decreases risk of breast cancer recurrence. Methods: We investigated the effects of lifestyle modifications (exercise only, or combined caloric restriction and exercise) on adipokines, IL-2, IL-6, IL-8, IL-10, CRP, and TNF-α biomarkers in breast cancer survivors. Searches were completed in June and July of 2019 to identify randomized controlled trials that met inclusion criteria. Weighted mean difference was calculated using random- or fixed- effects models based on the heterogeneity of the studies. Results: 2501 records were identified with 30 ultimately meeting inclusion criteria of the systematic review. 21 studies provided data suitable for meta-analysis. We observed leptin levels were significantly reduced in the exercise only group compared to sedentary control (WMD -5.66; 95% CI, -11.0 to -0.33, p = 0.04). Conclusion: Leptin may be a primary mediator of exercise-induced improvements in breast cancer recurrence. Impact: This is the first review and meta-analysis to examine combined exercise and caloric restriction programs in breast cancer survivors. Future studies should further examine combined programs and their efficacy for altering leptin.