Effects of exercise therapy on chemotherapy delivery and response in primary breast cancer: A secondary analysis of a randomized trial

Abstract Background Whether structured exercise therapy improves chemotherapy delivery, tolerability, and tumor response is unclear. Methods This was a secondary analysis of a phase 2 trial investigating exercise therapy ( n = 72) versus usual care ( n = 72) in patients with primary breast cancer. Exercise therapy comprised individualized treadmill walking three times weekly for 20–50 minutes per session at 55%–100% of pretreatment exercise capacity. Chemotherapy delivery was assessed according to the relative dose intensity (RDI), tolerability was assessed according to patient‐reported outcomes and blood laboratory values, and response was assessed based on the pathologic complete response rate in patients who received neoadjuvant chemotherapy. Results In the exercise therapy group, 51 patients (71%) reached 100% RDI (median, 100%; interquartile range, 100%–100%) compared with 41 patients (57%) in the usual care group (median, 100%; interquartile range, 95%–100%; p = .08). Tolerability was similar in both groups; the rates of grade 3 or higher neutropenia and anemia were 22% versus 39% and 7% versus 10% in the exercise and usual care groups, respectively. In patients who received anthracyclines ( n = 104), 41 (77%) had 100% chemotherapy RDI in the exercise therapy group versus 29 (57%) in the usual care group ( p = .026). In the neoadjuvant chemotherapy subgroup ( n = 51 tumors), the postneoadjuvant therapy (yp) pathologic complete response (ypT0ypN0) rate was 27% (95% confidence interval, 12%–50%) in the exercise therapy group compared with 28% (95% confidence interval, 13%–47%) in the usual care group ( p > .9). Conclusions In patients with primary breast cancer, exercise therapy was associated with improved delivery of anthracycline‐based chemotherapy. Although exercise therapy was not significantly associated with tumor response, effects varied by tumor subtype (trial registration: Clinicaltrials.gov identifier NCT01943695).