Endometrial Carcinoma and Hormone Replacement Therapy

The relationship between unopposed estrogen use and endometrial cancer has been firmly established over the last 30 years by numerous experimental and epidemiological studies (1-6). The relative risks from different studies vary widely: the overall estimated increase in relative risk for users compared with nonusers from a recent meta-analysis was reported as 2.3 [95% confidence interval (CI) 2.1-2.5], with a much higher risk ratio (RR) associated with prolonged duration of use (RR 9.5 for 10 or more years) (7). Unsurprisingly, the incidence of endometrial hyperplasia is increased in postmenopausal women on unopposed estrogen therapy, with an incidence of approximately 15-20% per year (3,8,9).