Exercise as anticancer medicine? Evidence, mechanisms and implementation in oncology.

Research over the past two decades has repositioned exercise from a general lifestyle recommendation to a potential anticancer intervention. Pooled analyses of more than 1.4 million participants link regular physical activity with lower incidence of at least 13 tumour types, and prospective cohort data report cancer-specific mortality 24-31% lower among the most active patients with breast, colorectal, prostate and lung cancer, although these estimates derive from observational designs using self-reported activity. In 2025, a phase III trial in stage III colon cancer provided the first randomised evidence that a structured exercise and behaviour-change programme improves disease-free and overall survival after adjuvant chemotherapy; a randomised trial in ovarian cancer subsequently did not show a progression-free survival benefit. Candidate mechanisms include insulin and growth-factor signalling, myokine secretion, immune mobilisation, reduced chronic inflammation and gut microbiome remodelling, although these rest on evidence ranging from cell culture to human trials and are rarely distinguished by level. Despite this evidence, structural, educational and economic barriers prevent integration of exercise into routine oncology care. This Review synthesises the available evidence and identifies the steps required for clinical adoption.