The impact of postdiagnosis/pretreatment exercise on distant recurrence-free interval in breast cancer patients is a function of subtype and menopausal status, as shown by new data recently published on The Journal of Clinical Oncology.

This multicenter prospective cohort analysis was conducted on 10359 patients with primary breast cancer enrolled in the french CANcer TOxicities study between 2012 and 2018, with follow-up through October 2021; since postdiagnosis exercise is associated with lower breast cancer  mortality, the study aimed to investigate the impact and dose- response relationship of exercise and distant recurrence-free interval. Results showed a non linear association between exercise and recurrence: increasing exercise ≥ 5 metabolic equivalent of task–hours per week (MET-h/wk) was associated with an inverse linear reduction in recurrence events up to approximately 25 MET-h/wk; increasing exercise over this threshold did not provide any additional benefit. Stratification by subtype revealed that the most responsive subtypes were HR-/HER2- and HR-/HER2+ tumors; premenopausal women were also more responsive to exercise. As authors conclude, «Our data suggest the hypothesis that exercise doses below and above a homeostatic zone (therapeutic range) confer suboptimal recurrence benefit, and potential antitumor effects of exercise may be confined to only certain subtypes in primary breast cancer. Early-phase trials evaluating whether exercise therapy has biologic antitumor activity and whether activity differs as a function of tumor molecular features are required to guide the design of larger definitive trials».