Recreational physical activity, body mass index, and survival in women with colorectal cancer

Background and purpose: Previous studies have shown that physical inactivity and obesity are risk factors for the development of colorectal cancer. However, controversy exists regarding the influence of these factors on survival in colorectal cancer patients. We evaluated the impact of recreational physical activity and body mass index (BMI) before and after colorectal cancer diagnosis on disease-specific mortality and all-cause mortality. Patients and methods: This prospective cohort study included 1,339 women enrolled in the Women's Health Initiative study who were diagnosed with colorectal cancer subsequent to study enrollment. BMI and recreational physical activity were measured before cancer diagnosis at study entry (pre-diagnostic) and after diagnosis at study follow-up interviews (post-diagnostic). We used Cox regression to estimate the association between pre- and post-diagnostic exposures and survival after colorectal cancer diagnosis. Results: Among women diagnosed with colorectal cancer, 265 (13 %) deaths occurred during a median study follow-up of 11.9 years, of which 171 (65 %) were attributed to colorectal cancer. Compared with women reporting no pre-diagnostic recreational physical activity, those reporting activity levels of ≥18 MET-h/week had significantly lower colorectal cancer-specific mortality (hazard ratio (HR) = 0.68; 95 % confidence interval (CI): 0.41-1.13) and all-cause mortality (HR = 0.63; 95 % CI: 0.42-0.96). Similar inverse associations were seen for post-diagnostic recreational physical activity. Neither pre- nor post-diagnostic BMI were associated with mortality after colorectal cancer diagnosis. Conclusion: Recreational physical activity before and after colorectal cancer diagnosis, but not BMI, is associated with more favorable survival.