Association of Metformin, Other Antidiabetic Medications, and Statins With Incidence of Colon Cancer in Patients With Type 2 Diabetes

Background: Metformin and statins may have anticancer effects, with plausible cellular mechanisms. However, the association of these agents with the risk of colorectal cancer is unclear.

Patients and methods: This was a retrospective cohort study on a large population (N = 316,317) of patients with type 2 diabetes. Data were obtained from the Diabetes in Finland database (FinDM). In a full cohort analysis, hazard ratios (HRs) with their 95% confidence intervals (CIs) for ever use versus never use were estimated using a multiple Poisson regression model. A nested case-control design within the cohort was used to examine the association of colon cancer (CC) with the defined daily dose of medication. The data were analyzed by conditional logistic regression. The analyses were adjusted for the patient's age, sex, and duration of diabetes.

Results: In total, 1351 CC cases were diagnosed during 1996-2011. The results revealed insufficient evidence for an association between metformin (HR, 1.01; 95% CI, 0.90-1.14), other oral antidiabetic medications (HR, 1.05; 95% CI, 0.93-1.19), insulin (HR, 1.02; 95% CI, 0.86-1.22), or statins (HR, 0.94; 95% CI, 0.84-1.05) and the incidence of CC in the full cohort analysis. The results from the case-control study were similar, with no consistent trend in the incidence of CC according to the cumulative dose of metformin or the other studied medications.

Conclusion: This study found insufficient evidence for an association between metformin, insulin, other oral type 2 diabetes medications, or statins and the incidence of CC.