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 after treatment for breast cancer, and it is associated with increased treatment-induced toxicity, shorter time to tumor progression, and decreased survival. Exercise training is a potential intervention for maintaining or increasing LBM. We conducted a systematic review and a meta-analysis to investigate the effects of exercise training on LBM in breast cancer. METHODS: A comprehensive search was performed to November 2020 for randomized controlled trials reporting the effects of structured exercise training on LBM compared with control in women with breast cancer during or after 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 with control on LBM (0.58 kg, 95% confidence interval = 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 after (0.66 kg) cancer treatment. Exercise training was beneficial in studies enrolling postmenopausal women (0.58 kg) as well as in those with participants of mixed menopausal status (1.46 kg). CONCLUSIONS: Compared with usual care, exercise training has a beneficial effect on LBM in women with breast cancer, both during and after 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.