Antidiabetic medication, statins and the risk of endometrioid endometrial cancer in patients with type 2 diabetes

Objective To gain further evidence of an association between the incidence of endometrial cancer (EC) and the use of metformin, other antidiabetic medication (ADM) and statins in women with type 2 diabetes (T2D). Methods A retrospective cohort of 92,366 women with newly diagnosed T2D was obtained from a diabetes register (FinDM). 590 endometrioid ECs were observed during the follow-up time. Poisson regression was utilized to estimate the hazard ratios (HRs) with 95% confidence intervals (95% CIs) of the endometrioid EC in relation to the use of metformin, other oral ADM, insulin and statins. Nested case-control analyses were performed, where up to 20 controls were matched for age and duration of DM for each EC case. The HRs were estimated by conditional logistic regression for never/ever and cumulative use of different forms of ADM and statins. Results In the case-control analyses the use of metformin (HR 1.24, 95% CI 1.02–1.51) and other oral ADM (HR 1.25, 95% CI 1.04–1.50) was associated with an increased incidence of endometrioid EC compared to no ADM use. No difference was observed between metformin users and those using other oral ADMs. The use of statins was inversely related to the incidence of endometrioid EC (HR 0.78, 95% CI 0.65–0.94). Results from the full cohort analysis supported this finding. Conclusions In our study the use of metformin or other oral forms of ADM was not associated with a lowered risk of endometrioid EC in women with T2D. Instead statins were observed to be inversely associated with endometrioid EC in this population.