Prediagnostic physical activity and colorectal cancer survival: Overall and stratified by tumor characteristics

Background: Physical activity is associated with a lower incidence of colorectal cancer; however, the relationship of physical activity with colorectal cancer survival is not yet clear. We evaluated the association between prediagnostic physical activity and colorectal cancer survival, overall and accounting for tumor markers associated with colorectal cancer survival: BRAF and KRAS mutation status and microsatellite instability (MSI) status. Methods: Participants were 20- to 74-year-old colorectal cancer patients diagnosed between 1998 and 2007 from the populationbased Seattle Colon Cancer Family Registry (S-CCFR). Selfreported physical activity in the years preceding colorectal cancer diagnosis was summarized as average metabolic equivalent task hours per week (MET-h/wk; n = 1,309). Somatic BRAF and KRAS mutations and MSI status were evaluated on a subset of patients (n = 1043). Cox regression was used to estimate HRs and 95% confidence intervals (CI) for overall and disease-specific survival after adjusting for relevant confounders. Stratified analyses were conducted across categories of BRAF, KRAS, and MSI, as well as tumor stage and site. Results: Higher prediagnostic recreational physical activity was associated with significantly more favorable overall survival (HR for highest vs. lowest category, 0.70; 95% CI, 0.52-0.96); associations were similar for colorectal cancer- specific survival. Results consistently indicated a favorable association with physical activity across strata defined by tumor characteristics. Conclusion: Individuals who were physically active before colorectal cancer diagnosis experienced better survival than those who were inactive or minimally active. Impact: Our results support existing physical activity recommendations for colorectal cancer patients and suggest that the beneficial effect of activity is not specific to a particular molecular phenotype of colorectal cancer.