12-week resistance training and body composition in women survivors of breast cancer: influence of tumour type and treatments

Objective To assess the effects of a 12-week resistance training intervention on body composition in female breast cancer survivors. The secondary exploratory aim was to evaluate whether tumour type and treatment received were associated with changes in body composition following the intervention. Methods The Ejercicio FÍsico para supervivientes de CÁNcer de mama (EFICAN) trial recruited 60 volunteer women survivors of breast cancer who completed chemotherapy, radiotherapy and/or surgery and were randomly assigned to either a 12-week exercise-based intervention group (IG; two exercise sessions/week plus ≥10 000 steps/day) or a control group (CG; ≥10 000 steps/day). Baseline and postintervention assessments of body composition (ie, fat and muscle, fat percentage and visceral fat level) were conducted using a bioelectrical impedance device. Results No significant between-group differences were observed in fat mass, muscle mass, fat percentage or visceral fat level. The exploratory analyses showed that participants who received chemotherapy experienced unfavourable changes in these outcomes (all p<0.05). However, the subgroup analyses revealed that while the participants in the CG who received chemotherapy (n=21) experienced an increase in fat mass (B=2.062 kg, p=0.045), body fat percentage (B=3.052%, p=0.004) and visceral fat mass (B=1.262 kg, p=0.017), the participants in the IG who received chemotherapy (n=24) did not present such negative changes in body composition. Conclusions The EFICAN intervention that combined resistance training with home-based physical activity did not lead to significant changes in body composition in comparison to home-based physical activity alone. Although the tumour type and hormone therapy were not associated with changes in body composition, receiving chemotherapy was associated with a deterioration in body composition only in the CG. Trial registration number ISRCTN14601208 .