Colorectal cancer in patients with type 2 diabetes mellitus: a single-center experience

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of colorectal cancer (CRC). The aim of the study is to evaluate the prevalence of CRC in a cohort of Caucasian patients with T2DM and the association with other variables previously known to be related with increased risk of CRC. We retrospectively evaluated the data of 741 consecutive Caucasian patients with T2DM who underwent colonoscopic screening in our tertiary referral center. A control cohort of 333 patients with thyroid disease was selected to evaluate the difference in the incidence of CRC. At a median follow-up of 132.5 months (range 33.3-175.7), 67 cases of cancer (prevalence 9%) occurred; among these, 14 cases of CRC were reported (prevalence 1.88%) among the diabetic patients, while only two case (one of these was a CRC) (overall prevalence 0.006%, prevalence of CRC 0.003%) occurred in the control group; the difference between the prevalence of CRC was statistically significant (chi-square 4.21, p=0.04). The median duration of T2DM to CRC diagnosis was 168 months (range 12-768). At the univariate analysis, older age (p=0.001, r 0.138) and diabetes duration (p=0.001, r 0.138) were related to higher risk of cancer, while metformin seems to be protective towards cancer (p=0.07, r -0.098). In the subset of patients with CRC, the age (RR = 2.25; 95% CI: 0.30 - 17.31; p less than 0.001), the diabetes duration (RR = 1.93; 95% CI: 0.25 – 14.77; p = 0.001) and the sulphonylureas treatment (RR = 2.33; 95% CI: 0.78 – 7.38; p = 0.007) were independently correlated with CRC. In our study, the prevalence of CRC in the cohort of patients with T2DM was higher compared to that from the National Tumor Register in 2010 (0.5%). Furthermore, we could speculate that sulphonylureas may play a role in CRC carcinogenesis impairing the physiological insulin secretion.