Metformin, Statins Not Linked With Ovarian Cancer Risk in Diabetic Patients

A large retrospective cohort study found no association between the use of metformin or statins and the incidence of ovarian cancer in women with type 2 diabetes.

“People who have type 2 diabetes have been reported to have an increased incidence of various cancers, including ovarian cancer, compared with those without diabetes, the risk being highest in insulin-treated patients,” wrote study authors led by Elina Urpilainen, of the University of Oulu in Finland. Metformin, commonly used to treat type 2 diabetes, has been linked with lower incidence of several cancer types, including ovarian cancer. Statins, widely used to treat the cardiovascular diseases associated with type 2 diabetes, also may have a cancer protective effect.

The new study examined these potential effects in a cohort of 137,643 women over 40 years old and diagnosed with type 2 diabetes in Finland between 1996 and 2011; it covered a total follow-up of 748,282 person-years at risk, with a mean follow-up of 5.4 years. The results were published in BJOG: An International Journal of Obstetrics and Gynaecology.

Over the follow-up period, 303 women were diagnosed with epithelial ovarian cancer. The incidence rate was highest in the oldest age group (60–69 years), at 51.4 per 100,000 person-years, and in the group with the longest duration of diabetes (5–8 years), at 52.5 per 100,000 person-years.

The investigators conducted a case-control analysis that included 6,060 controls matched for age and type 2 diabetes duration with the 303 cancer cases. Approximately two-thirds of both cases and controls were ever-users of metformin, and just over 50% were ever-users of statins.

In the full cohort, metformin use had a hazard ratio (HR) for ovarian cancer of 1.02 (95% CI, 0.72–1.45). In the case-control analysis, the HR was 0.91 (95% CI, 0.61–1.34). For statins, in the full cohort, the HR for ovarian cancer was 0.99 (95% CI, 0.78–1.25), and in the case-control analysis it was 0.96 (95% CI, 0.75–1.23). For insulin use, the HR in the full cohort was 1.19 (95% CI, 0.73–1.93), and in the case-control analysis it was 1.19 (95% CI, 0.72–1.97). The authors noted that there was also no trend with respect to rising cumulative use of metformin or statins.

They also pointed out several limitations to the study, including a lack of information on family history, parity of the women included, and data on BMI or other markers of insulin resistance. Still, the comprehensive national registers used are considered very reliable, they noted.

“We found no evidence of an association between metformin or other forms of oral antidiabetic medication and the incidence of epithelial ovarian cancer in women aged 40 years or older with type 2 diabetes,” they concluded.