Physical exercise during neoadjuvant chemotherapy for breast cancer as a mean to increase pathological complete response rates: Trial protocol of the randomized Neo-ACT trial.

Introduction: In early breast cancer, neoadjuvant chemotherapy (NACT) is increasingly used. The proof of efficacy is pathologically complete response (pCR), i.e. the absence of invasive tumour in breast and lymph nodes at surgery. Today, pCR is a common endpoint in pharmaceutical trials since it is significantly associated with survival especially in triple-negative and HER2-positive subtypes. Apart from the mitigation of treatment-related toxicity and symptoms, physical exercise mediates anti-tumoral systemic effects associated with tumour regression in preclinical and clinical models. The aim of Neo-ACT is to test the hypothesis that physical exercise can improve pCR rates in breast cancer patients receiving NACT.

Method: The Neo-ACT trial is a prospective clinical trial, randomising T1-3N0-2 breast cancer patients planned for NACT to either a home-based physical exercise intervention supported by a mobile application or routine care. The primary endpoint is pCR; secondary endpoints are patient-reported quality of life, toxicity-related outcomes, and oncological outcomes such as Residual Cancer Burden, objective radiological tumour response, as well as overall, breast cancer-specific and disease-free survival at 2, 5 and 10 years. The intervention consists of a combination of high-intensity interval and resistance training of progressing intensity, and includes at least 150 min of moderate to vigorous physical activity per week, inclusive of two weekly 60-min exercise sessions. In order to show an improvement in pCR of 10%, a total of 712 participants need to be included in the analysis. The Neo-ACT has been registered at clinicaltrials.gov on January 11, 2022 (NCT05184582).

Expected Results: If Neo-ACT can prove the oncological efficacy of physical exercise, implementation of training programmes into NACT schedules will be pursued. The use of a digitally led exercise intervention aims to test the potential of such a strategy for use in rural areas and areas of limited resources.