Prediagnostic physical activity and colorectal cancer survival: overall and stratified by tumor characteristics
A partir des données d'un registre américain des cancers familiaux portant sur 1 309 patients atteints d'un cancer colorectal diagnostiqué entre 1998 et 2007, cette étude évalue l'association entre une activité physique avant le diagnostic et la survie des patients, en fonction des caractéristiques de la tumeur et la présence de mutations des gènes BRAF et KRAS
Background: Physical activity is associated with a lower incidence of colorectal cancer (CRC); however, the relationship of physical activity with CRC survival is not yet clear. We evaluated the association between pre-diagnostic physical activity and CRC survival, overall and accounting for tumor-markers associated with CRC survival: BRAF and KRAS mutation status and microsatellite instability (MSI) status. Methods: Participants were 20-74 year old CRC patients diagnosed between 1998 and 2007 from the population-based Seattle Colon Cancer Family Registry (S-CCFR). Self-reported physical activity in the years preceding CRC diagnosis was summarized as average metabolic equivalent-task hours per week (MET-h/week) (n=1309). Somatic BRAF and KRAS mutations and MSI status were evaluated on a subset of patients (n=1043). Cox regression was used to estimate hazard ratios (HR) 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 pre-diagnostic 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 CRC-specific survival. Results consistently indicated a favorable association with physical activity across strata defined by tumor characteristics. Conclusion: Individuals who were physically active prior to CRC diagnosis experienced better survival than those who were inactive or minimally active. Impact: Our results support existing physical activity recommendations for CRC patients and suggest that the beneficial effect of activity is not specific to a particular molecular phenotype of CRC.