Background: Physical exercise is recommended to cancer patients. We aim to evaluate the efficacy of a low-cost community-based supervised exercise program in early breast cancer survivors after primary treatment. Methods: A single-arm clinical trial, controled by a run-in period, of a 16-weeks intervention consisting of 3 weekly sessions of combined aerobic and strength exercise at moderate to vigorous intensity in group classes of no more than 20 participants. Participants were evaluated at weeks 1, 8 and 16 (M1, M2 and M3) of the run-in period and 8 and 16 of the experimental phase (M4 and M5) for quality of life (QoL) (EORTC QLQ-C30), handgrip strength, sit-to-stand (STS) test and maximal aerobic capacity. Results: Of the 82 participants, 25 completed the program and evaluations. Median age was 58 years (39-73), 64% underwent mastectomy, 48% had axillary lymph node dissection, 80% was treated with radiotherapy, 80% with chemotherapy and 84% with hormonotherapy. Median time from surgery was 13 months (4-107). Physical functioning domain of QoL improved significantly following 8 (p = 0.04) and 16 weeks (p = 0.03) of exercise training. Handgrip strength in surgical and non-surgical limbs increased after 8 weeks and maintained after 16 weeks of control phase, further increasing after 8 weeks (p = 0.01) and 16 weeks of exercise (p = 0.00). Lower-limb strength also increased after 16 weeks of exercise (p = 0.01), and maintained during control (p = 0.09). Additionally, maximal aerobic capacity tended to further increase after exercise training (p = 0.06), after increasing during control phase (p = 0.02). Conclusions: A low-cost community-based supervised exercise program improves physical fitness and functioning in breast cancer survivors after primary treatment. Clinical trial information: NCT04024280.

Results were tested with repeated measures analysis of variance or Friedman and Wilcoxon tests when appropriate and are presented as mean±SD; *Higher than M1, p< 0.05; ** Higher than M3, p< 0.05; † Higher than M1; p< 0.01; ‡ Higher than M3; p< 0.01.