Excess Body Weight Is Not Associated with Colorectal Cancer Survival: The Multiethnic Cohort

Abstract

PurposeExcess body weight has been associated with a higher risk for colorectal cancer (CRC) and may also adversely affect mortality in CRC patients. The current study examined the relation of prediagnostic body mass index (BMI) with CRC‐specific and all‐cause mortality in the Multiethnic Cohort (MEC).MethodsAmong the 5 major ethnic groups, 4204 invasive cases of CRC were diagnosed between cohort entry and 2010. Cox regression was applied to estimate hazard ratios (HR) and 95% confidence intervals (CI) while adjusting for relevant covariates. Using self‐reports at baseline and after 5.7±0.8 years (73% of participants), BMI was treated as time‐varying exposure.ResultsOf the 2258 men and 1946 women, 1674 (40%) were overweight and 939 (22%) were obese at baseline. After 6.0±4.7 years of follow‐up, 1976 overall deaths and 1095 deaths due to CRC occurred. No significant association with CRC‐specific mortality was detected in men (HR=0.94; 95%CI: 0.84, 1.04) and women (HR=0.98; 95%CI: 0.89, 1.08) per 5 units of BMI. In men, all‐cause mortality showed no relation with BMI (HR=0.97; 95%CI: 0.90, 1.06), whereas it was elevated in women (HR=1.10; 95%CI: 1.03, 1.31). Interactions of BMI with ethnicity were not significant, but risk estimates varied across groups.ConclusionsLittle evidence for an adverse effect of excess body weight on survival was detected within a multiethnic group of CRC cases although some variations in mortality were seen after stratification by sex and ethnicity.