260 Exogenous Insulin and Risk of Colorectal Adenomas in Type I Diabetes

Abstract

INTRODUCTION: The recent update for colorectal cancer screening to begin earlier at the age of 45 reinforces the need to better risk stratify populations for screening of colorectal adenomas which are precursor lesions to tumor formation. Prior studies suggest an association between Type II diabetes and risk of colon cancer with the underlying theory that progressive insulin insensitivity in addition to insulin use leads to hyperinsulinemia which promotes colorectal carcinogenesis. There is lack of data on risk of adenomas with isolated exogenous insulin use which is reflected in Type 1 diabetes. In this single center retrospective study, we examined the adenoma detection rate in Type I diabetics to better delineate the isolated risk of exogenous insulin use on developing colon cancer. METHODS: Charts for Type 1 diabetic patients spanning the age of 30–80 were reviewed. Age at first colonoscopy, gender, race, BMI, smoking history, family history of colon cancer, number of polyps, insulin use, and HbA1c were collected. Age and gender matched non-diabetics were used as control. To further control for confounding factors, multivariate analysis using logistic regression was performed. RESULTS: As only 5% of diabetics are Type 1, our preliminary results included forty-eight Type 1 diabetics matched with respective controls who underwent colonoscopy. Multivariate analysis showed a significant difference in adenoma detection rate between control and Type 1 diabetics (33% vs 52%, P = 0.017; OR 3.25; CI 1.28–8.95). This difference was significant (P = 0.033) in both the younger age group (<60 years of age) and the older age group (60–80 years of age). Within the Type 1 diabetes group, there was no significant association between adenoma detection and HbA1c level. There was also independent association between adenoma detection and male gender (P = 0.041), increased age (P = 0.052), and positive smoking history (P = 0.098) which is consistent with previously known data. CONCLUSION: Our study thus far suggests that Type 1 diabetics have an increased risk of colorectal adenomas spanning a wide range of age groups and that this difference is not affected by the HbA1c level, which is a marker of insulin resistance. Having controlled for a variety of factors, our findings suggest that this increased risk of adenomas may be influenced by long-term exogenous insulin use, as Type 1 diabetics become reliant on this at an early age. These findings will be tested for validation in a larger cohort.