Endometrial cancer risk with menopausal hormone therapy: Health Insurance Database in South Korea‐based cohort study

To determine the risk of endometrial cancer according to the types of menopausal hormones used.This retrospective cohort study recruited postmenopausal women older than 40 years from 2003 to 2011, utilizing data from the Korean national health insurance system from 2002 to 2019. The menopausal hormone therapy (MHT) group consisted of women who had been prescribed MHT for greater than 6 months between 2003 and 2011. The non-MHT group consisted of women who had never used menopausal hormones between 2003 and 2011.A non-MHT group of 1 000 550 women and a MHT group of 353 025 women were chosen. In comparison to never-users, the risk of endometrial cancer was not higher in women who reported last using tibolone (adjusted hazard ratio [aHR] 1.08, 95% confidence interval [CI] 0.96-1.2), combined estrogen plus progestin by the manufacturer (aHR 0.83, 0.72-0.96), combined estrogen plus progestin by the physician (aHR 0.88, 0.7-1.12), and transdermal estrogen (aHR 1.13, 0.36-3.52).Tibolone, combined estrogen plus progestin by the physician, and transdermal estrogen do not affect the risk of endometrial cancer. The combination of estrogen plus progestin by the manufacturer decreases the risk of endometrial cancer.