Diabetes Mellitus and Colorectal Neoplasia.

BACKGROUND Many studies have provided evidence for an association between obesity, physical inactivity, and western diet as risk factors for colorectal cancer (CRC). Few studies directly address the association between type 2 Diabetes Mellitus (DM) and the risk of colorectal lesions at specific anatomic locations. METHODS 2,663 subjects with a previous history of adenoma(s) and removal of all current adenomas at study entry were followed for a mean time of three years across three different chemoprevention clinical trials. The primary endpoint was colorectal adenoma recurrence and number of lesions during the treatment phase; the secondary endpoints were presence of advanced colorectal neoplasia (CRN) and location of CRN. Using log linear regression, the effect of DM status on the relative risk (RR) of CRN recurrence, advanced CRN, and location of CRN was assessed. RESULTS DM status was not significantly associated with incidence of colorectal adenomas, incidence of advanced colorectal lesions, or left-sided colorectal neoplastic lesions. Subjects with DM had a marginally increased risk of right-sided (p= 0.06) colorectal adenomas and a significant increased risk of multiple right-sided adenomas (p=0.03) in the unadjusted model; this association was not significant after adjusting for age and other potential confounders (RR=1.22, 95% CI: 0.85-1.76). CONCLUSION We did not observe a statistically significant increased risk in CRN recurrence for overall neoplasia, advanced neoplasia or location of neoplasia in individuals with DM compared to non-DM individuals. However, given the patterns observed in this investigation, future studies with longer follow-up time and longer DM exposure, incorporating objective measurements of type 2 DM might help elucidate the risk of CRN among individuals with DM.