The association of diabetes with colorectal cancer risk: The Multiethnic Cohort

Abstract

Background:Diabetics have been found to have a greater risk of colorectal cancer than non-diabetics.Methods:We examined whether this relationship differed by ethnic group, cancer site or tumour stage in a population-based prospective cohort, including 3549 incident colorectal cancer cases identified over a 13-year period (1993-2006) among 199 143 European American, African American, Native Hawaiian, Japanese American and Latino men and women in the Multiethnic Cohort.Results:Diabetics overall had a significantly greater risk of colorectal cancer than did non-diabetics (relative risk (RR)1.19, 95% confidence interval (CI)1.09-1.29, P-value (P)0.001). Positive associations were observed for colon cancer, cancers of both the right and left colon, and cancers diagnosed at a localised and regional/distant stage. The association with colorectal cancer risk was significantly modified by smoking status (P Interaction 0.0044), with the RR being higher in never smokers (RR1.32, 95% CI1.15-1.53, P0.001) than past (RR1.19, 95% CI1.05-1.34, P0.007) and current smokers (RR0.90, 95% CI0.70-1.15, P0.40).Conclusion:These findings provide strong support for the hypothesis that diabetes is a risk factor for colorectal cancer. © 2010 Cancer Research UK All rights reserved.