Association between physical activity and the time course of cancer recurrence in stage III colon cancer

OBJECTIVE: We determined if postoperative physical activity prevents or delays cancer recurrence in patients with stage III colon cancer. METHODS: This cohort study nested within a randomised trial enrolled 1696 patients with surgically resected stage III colon cancer. Physical activity was calculated based on self-reporting during and after chemotherapy. Patients were classified as physically active (≥9 MET-h/wk, comparable with the energy expenditure of 150 min/wk of brisk walking, consistent with the current physical activity guidelines for cancer survivors) or physically inactive (<9 MET-h/wk). The confounder-adjusted hazard rate (risk of recurrence or death) and HR by physical activity category were estimated with continuous time to allow non-proportionality of hazards. RESULTS: During a median 5.9 years follow-up, 457 patients experienced disease recurrence or death. For physically active and physically inactive patients, the risk of disease recurrence peaked between 1 and 2 years postoperatively and declined gradually to year 5. The risk of recurrence in physically active patients never exceeded that of physically inactive patients during follow-up, suggesting that physical activity prevents—as opposed to delays—cancer recurrence in some patients. A statistically significant disease-free survival benefit associated with physical activity was observed during the first postoperative year (HR 0.68, 95% CI 0.51 to 0.92). A statistically significant overall survival benefit associated with physical activity was observed during the first three postoperative years (HR 0.32, 95% CI 0.19 to 0.51). CONCLUSIONS: In this observational study of patients with stage III colon cancer, postoperative physical activity is associated with improved disease-free survival by lowering the recurrence rate within the first year of treatment, which translates into an overall survival benefit.