Polycystic ovary syndrome and endometrial cancer risk: results from a nationwide cohort study.

Most previous studies found an elevated risk of endometrial cancer among women with polycystic ovary syndrome (PCOS). However, these had highly varying methods for ascertainment of PCOS diagnoses and limitations such as few exposed women and short follow-up. In this cohort study, we investigated the association between PCOS and endometrial cancer among women born in Denmark between January 1, 1940, and December 31, 1993 (n = 1 719 121). Data in this study, including PCOS and endometrial cancer diagnoses and covariates, were derived from nationwide registers. We used Cox proportional hazards regression models to calculate hazard ratios (HRs) and 95% CIs. A total of 7862 endometrial cancer cases were identified during 23.7 years of follow-up (IQR, 37.7-61.9). We found an increased risk of endometrial cancer among women with PCOS compared with women without PCOS (HR = 3.02; 95% CI, 2.03-4.49). The risk was increased for premenopausal women (HR = 5.82; 95% CI, 3.64-9.30), whereas no marked association was seen for postmenopausal women. However, for postmenopausal women, results were limited by few cases and young age at the end of follow-up. Mounting evidence of an increased risk for endometrial cancer among women with PCOS reinforces the need for prevention and early detection. This article is part of a Special Collection on Gynecological Cancers.