Reduced risk of prostate cancer in a cohort of Lithuanian diabetes mellitus patients.

Abstract

130 Background: An inverse association has been shown between diabetes and prostate cancer risk. The aim of this study was to determine whether type 2 diabetes mellitus (T2DM) and metformin is associated with prostate cancer risk. Methods: A retrospective cohort design was used to examine the relationship between diabetes and prostate cancer risk. The cohort was composed of male patients identified with diagnosis of T2DM in the National Health Insurance Fund database during 2000–2016. Cancer cases were identified by record linkage with the Lithuanian Cancer Registry which is a nationwide population-based cancer registry that contains personal and demographic information, as well as information on diagnosis of all people diagnosed with cancer in Lithuania since 1978. We calculated standardized incidence ratios (SIRs) for prostate cancers as a ratio of observed number of cancer case in people with diabetes diagnosis to the expected number of cancer cases in the underlying general population. Results: Overall, 68,449 males were diagnosed with diabetes in Lithuania between 2000 and 2016 were included in final cohort. 2,754 prostate cancers were observed versus 3,111.26 expected within a period of observation entailing an SIR of 0.89 (95% CI: 0.85–0.92). Significantly lower risk of prostate cancer was found in diabetic patients in all age groups, there were no differences in prostate cancer risk by time since diabetes diagnosis. Significantly lower risk of prostate cancer also was found in both metformin users and never-users groups, with higher risk reduction in metformin users (SIR 0.71, 95% CI: 0.68–0.75) than in T2DM patients never-users (SIR 0.88, 95% CI: 0.80–0.96). Conclusions: In the large population-based study we found significantly decreased risk of prostate cancer among men with T2DM. Our study suggests that metformin use in patients with T2DM may be associated with reduced risk of developing prostate cancer.