Physical activity during anthracycline chemotherapy: exploratory secondary analysis of a randomized trial of functional capacity, free-living activity, and ejection fraction

Background: Anthracycline-based chemotherapy produces progressive functional decline and cardiotoxicity in adults with cancer. Physical activity interventions may attenuate these effects, yet evidence across multiple domains remains limited. Objectives: To compare trajectories of Six-Minute Walk Distance (6MWD), daily steps, weekly MVPA, and ejection fraction (EF) across six months of chemotherapy and to explore whether step-volume change showed any preliminary association with functional capacity change. Methods: Secondary analysis of a pilot RCT ( N = 20). Linear mixed-effects models with Kenward-Roger adjusted EMMs were fitted for each outcome, controlling for age, sex, and race. Results: Adjusted 6MWD was higher in the PAI arm at 3 and 6 months in this pilot sample; the 6-month difference exceeded published minimally important difference estimates, but the estimate remains preliminary because of the small sample and exploratory design. Daily steps and MVPA were directionally higher in PAI. EF remained broadly within the normal range in both arms, but the sample was too small to draw safety or cardioprotection conclusions. Exploratory change-score analyses did not support step-volume change as a mediator of the functional-capacity findings. Conclusions: In this exploratory secondary analysis, individually prescribed physical activity showed more favourable functional-capacity trajectories; cardiac findings were inconclusive and do not support safety or cardioprotection conclusions. A larger, prospectively powered trial would be needed to confirm these exploratory findings and to test cardiac outcomes and mediation prospectively. Trial registration : Not applicable