It is well recognized that women with type 2 diabetes have an increased risk of endometrial (uterine) cancer.  There are various pharmacotherapy options for diabetes, including metformin and thiazolidinediones, which reduce insulin levels (insulin-sensitizing drugs), and secretagogues, which increase circulating insulin levels.  As hyperinsulinemia is recognized as a risk factor for the development of endometrial cancer, it was hypothesized that metformin could be associated with a lower risk of endometrial cancer compared to other medication types among women with diabetes.  We conducted a population-based study linking prescription data from PharmaNet with endometrial cancer cases from the BC Cancer Agency.  We had data on over 150,000 women who had been prescribed at least one diabetic medication in British Columbia from 1996 to 2009, and 556 women diagnosed with endometrial cancer from 2000-2009.

This study found that those who were prescribed metformin alone or with other insulin-sensitizing drugs did not have a lower risk of endometrial cancer compared to other drug types.  The patients who had the highest risk were prescribed all four major classes of medications (metformin, thiazolidinediones, secretagogues, and insulin, odds ratio 1.9, 95% CI 1.1-3.3).  This prescription history is in keeping with the poorest glycemic control, or the highest extent of insulin resistance, and this is likely the reason for the highest endometrial cancer risk, rather than the effect of any medication. This observation underscores the need to reduce the risk of diabetes in the first place, in order to circumvent other health consequences including endometrial cancer.

The full article can be found here: https://authors.elsevier.com/a/1UKNI62pzAEPZz