Risk of exogenous estrogen therapy and endometrial cancer.

A retrospective study was carried out on 431 patients with endometrial cancer and 431 control subjects matched as to age, race, and parity. They were seen at Duke University Medical Center from 1940 to 1975. The study was performed in order to evaluate the risk of exogenous estrogen therapy and the development of adenocarcinoma of the endometrium. The overall risk was 2.38, with certain subgroups demonstrating different degrees of risk. Increased risk was associated with estrogen therapy of longer than 5 years' duration in white patients. The risk also was confined to Stage I, grade 1 lesions and more superficial myometrial invasion. Five-year survival for patients who used estrogen replacement and had Stage I, grade 1 lesions was 94.7%. The risks associated with exogenous estrogens are real but should be considered in a risk/benefit context when prescribing for the needs of an individual patient.