The Effect of Exercise Training on Lean Body Mass in Breast Cancer Patients: A Systematic Review and Meta-analysis.

PURPOSE Reduced lean body mass (LBM) is common during and following treatment for breast cancer, and is associated with increased treatment-induced toxicity, shorter time to tumour progression and decreased survival. Exercise training is a potential intervention for maintaining or increasing LBM. We conducted a systematic review and meta-analysis to investigate the effects of exercise training on LBM in breast cancer. METHODS A comprehensive search was performed to November 2020 for randomised controlled trials reporting the effects of structured exercise training on LBM compared to control in women with breast cancer during or following cancer treatment. A random-effects meta-analysis was completed using the absolute net difference in the change in LBM between intervention and control groups as the outcome measure. Sensitivity and subgroup analyses were also performed. RESULTS Data from 17 studies involving 1743 breast cancer survivors were included in the meta-analysis. Overall, there was a significant benefit of exercise training compared to control on LBM (0.58 kg, 95% CI 0.27 to 0.88, p < 0.001). Subgroup analysis showed positive effects for resistance training (0.59 kg) and aerobic training (0.29 kg), and for exercise training conducted during (0.47 kg) or following (0.66 kg) cancer treatment. Exercise training was beneficial in studies enrolling post-menopausal women (0.58 kg) as well as in those with participants of mixed menopausal status (1.46 kg). CONCLUSION Compared with usual care, exercise training has a beneficial effect on LBM in women with breast cancer, both during and following cancer treatment. Given the physiological and functional importance of LBM in women with breast cancer, oncologists should encourage their patients to engage in regular exercise training, with particular emphasis on resistance training.