Effects of physical activity changes induced by behaviour change interventions on inflammation and patient-centred outcomes in breast cancer survivors: a systematic review

Purpose: Ample evidence supports using behaviour change interventions to increase physical activity (PA) in breast cancer survivors (BCSs). This systematic review aims to investigate if behaviour change intervention-induced changes in PA can modulate inflammation and improve patient-centred outcomes in this population. Methods: We searched six databases and synthesised evidence from 17 RCTs reporting between-group changes for inflammatory biomarkers, cancer-related fatigue (CRF), aerobic fitness, and/or quality of life (QoL). Results: Two RCTs reported small-to-medium effect size decreases in the ratios of IL-6:IL-10 and TNF-a:IL-10 at 12 weeks. Five RCTs reported significant intervention improvements in aerobic fitness; three trials further showed sustained intervention effects at two- and three-month follow-up. Four trials reported beneficial reductions in CRF post-intervention and three trials showed sustained intervention effects at follow-up. Three trials showed significant improvements in QoL at three and six months, with two trials demonstrating sustained intervention effects at two- and three-month follow-up. Further, six trials reported significant improvements in at least one QoL variable. Conclusion: We found limited but plausible evidence to support the beneficial effects of PA behaviour change interventions on inflammation and patient-centred outcomes in BCSs. Larger RCTs are particularly warranted to explore the causal impact on cytokine balance and possible mediating effects on patient-centred outcomes.