Purpose: Excess body weight is a risk factor for colorectal cancer (CRC) and may also adversely affect survival in CRC patients.
Methods: This study examined the relation of body mass index (BMI), which was self-reported at cohort entry and after 5.7 ± 0.8 years, with CRC-specific and all-cause survival among 4,204 incident cases of invasive CRC in the multiethnic cohort. Cox regression analysis with age as time metric and BMI as time-varying exposure was applied to estimate hazard ratios (HR) and 95% confidence intervals (CIs) while adjusting for relevant covariates.
Results: Over 6.0 ± 4.7 years of follow-up, 1,976 all-cause and 1,095 CRC-specific deaths were recorded. The mean time interval between cohort entry and diagnosis was 7.6 ± 4.7 years. No association with CRC-specific survival was detected in men (HR5units = 0.94; 95%CI 0.84-1.04) or women (HR5units = 0.98; 95%CI 0.89-1.08). In men, all-cause survival also showed no relation with BMI (HR5unit = 0.97; 95%CI 0.90-1.06), whereas it was reduced in women (HR5units = 1.10; 95%CI 1.03-1.18). Interactions of BMI with ethnicity were only significant for obesity. Obese Latino and overweight Native Hawaiian men as well as overweight African-American women experienced significantly better CRC-specific survival than whites. Overweight Japanese men and African-American women had better all-cause survival and obese Latino women had the lowest all-cause survival (HRobese = 1.74; 95%CI 1.08-2.80).
Conclusions: This analysis detected little evidence for an adverse effect of excess body weight on CRC-specific survival, but all-cause survival was reduced in women. These findings suggest that adiposity may be less important for CRC survival than as an etiologic factor.
Keywords: Colorectal cancer; Ethnicity; Obesity; Survival.