Review of epidemiologic studies of endometrial cancer and exogenous estrogen.

Epidemiologic literature on the association of exogenous estrogen and endometrial cancer is reviewed. Descriptive studies have documented fluctuations in the incidence of endometrial cancer, mainly of localized disease, associated with estrogen use. Etiologic studies have established an association between estrogen use during menopause and the occurrence of endometrial cancer. Although the association appears to be a valid one, several biases may have falsely increased the magnitude of this association. The association also appears to be strongest for local disease and weakest for the most invasive disease, which implies that the etiology for the more invasive endometrial cancers is largely unaccounted for by estrogen use. A need for a prospective study to define other potential risks and benefits of estrogen therapy is clear. However, appreciation of factors known to modify the risk of endometrial cancer from exogenous estrogen can help the clinician to use these preparations judiciously.