Moderators of the effects of exercise training in breast cancer patients receiving chemotherapy

BACKGROUND: Exercise training improves supportive care outcomes in patients with breast cancer who are receiving adjuvant therapy, but the responses are heterogeneous. In this study, the authors examined personal and clinical factors that may predict exercise training responses. METHODS: Breast cancer patients who were initiating adjuvant chemotherapy (N=242) were assigned randomly to receive usual care (UC) (n=82), resistance exercise training (RET) (n=82), or aerobic exercise training (AET) (n=78) for the duration of chemotherapy. Endpoints were quality of life (QoL), aerobic fitness, muscular strength, lean body mass, and body fat. Moderators were patient preference for group assignment, marital status, age, disease stage, and chemotherapy regimen. RESULTS: Adjusted linear mixed-model analyses demonstrated that patient preference moderated QoL response (P= .005). Patients who preferred RET improved QoL when they were assigned to receive RET compared with UC (mean difference, 16.5; 95% confidence interval 95% CI, 4.3-28.7; P= .008) or AET (mean difference, 11; 95% CI, -1.1-23.4; P= .076). Patients who had no preference had improved QoL when they were assigned to receive AET compared with RET (mean difference, 23; 95% CI, 4.9-41; P= .014). Marital status also moderated QoL response (P= .026), age moderated aerobic fitness response (P= .029), chemotherapy regimen moderated strength gain (P= .009), and disease stage moderated both lean body mass gain (P< .001) and fat loss (P= .059). Unmarried, younger patients who were receiving nontaxane-based therapies and had more advanced disease stage experienced better outcomes. The findings were not explained by differences in adherence. CONCLUSIONS: Patient preference, demographic variables, and medical variables moderated the effects of exercise training in breast cancer patients who were receiving chemotherapy. If replicated, these results may inform clinical practice.