The Impact of Sustained Metformin use on Survival in Diabetes Patients of Operable Colorectal Cancer: A Nationwide Cohort Study

Abstract BackgroundColorectal cancer is one of the most common cancers in the Western world and in Taiwan and the diabetes has been proven as an independent risk factor for incidence. Metformin, the drug of choice for the therapy of type 2 diabetes, has been shown to reduce the risk of developing colorectal cancer. Our study was investigated the impact of continuous use of metformin on the survival of diabetic patients after surgery for colorectal cancer.MethodsThis study identified 12,512 patients with colorectal cancer and type 2 diabetes who underwent curative surgery between 2000 and 2012 were collected from the Taiwanese population-based National Health Insurance Research Database. A total of 6,222 patients were included in the matched cohort, to adjust for differences in baseline variables. Time-dependent covariates in the cox proportional hazard model was used to examine the impacts of metformin use on survival.Results The average duration of follow-up was 49.4 months in the Metformin use group and 53.7 months in the non-Metformin use group. The Cox proportional hazard model revealed that continuous metformin use post operation was associated with 5-year survival benefit (HR: 0.23, 95% CI: 0.20-0.26). Furthermore, continuous metformin use also showed a benefit of decreasing liver metastases (HR: 0.83, 95% CI: 0.71-0.97).ConclusionsSustained Metformin use is associated with a significant survival benefit in diabetic colorectal cancer patients after operation, suggesting a potential anti-tumorigenic effect. Moreover, there was also a benefit of decreasing liver metastases in patients who received continuous metformin use.