Insulin therapy and colorectal adenoma risk among patients with type 2 diabetes mellitus: A case-control study in Korea

PURPOSE: Patients with Type 2 diabetes mellitus may be at increased colorectal adenoma and cancer risk. Moreover, chronic insulin therapy may increase the risk of colorectal cancer among patients with Type 2 diabetes mellitus. We investigated to determine whether insulin therapy might increase the risk of colorectal adenoma among clinically confirmed patients with Type 2 diabetes mellitus. METHODS: We conducted a retrospective study among patients with Type 2 diabetes mellitus who underwent total colonoscopy between January 2003 and July 2006 at Hallym University Sacred Heart Hospital. Among them (n=325), patients with histologically confirmed colorectal adenomas (n=100) and the same number of controls matched by age and sex were selected and analyzed. RESULTS: Adenoma cases showed significantly higher rate of chronic insulin therapy (more than 1 year) than controls (P=0.018). In multivariate regression analysis, patients who received chronic insulin therapy had three times the risk of colorectal adenoma compared with patients who received no insulin (odds ratio, 3; 95 percent confidence interval, 1.1-8.9; P=0.04). CONCLUSIONS: Chronic insulin therapy was associated with increased colorectal adenoma risk among Type 2 diabetes mellitus patients. This result may provide a need for more intensive colorectal cancer screening program in patients with Type 2 diabetes mellitus, especially those who receive chronic insulin therapy.