The effect of the duration of progestin use on the occurrence of endometrial cancer in postmenopausal women.

Abstract

Women who have ever used estrogen replacement therapy (ERT), even at a low dose, have an increased incidence of endometrial cancer. The addition of a progestin to ERT reduces the incidence of endometrial cancer. The duration of progestin administration is more important than the dose. A MEDLINE review of the literature was performed using the search terms endometrial cancer, epidemiology, and hormone replacement therapy (HRT). Women who have ever used ERT have an increased incidence of endometrial cancer. The use of HRT for more than 5 years, with a progestin use of <10 days per cycle, has a relative risk = 1.8. Continuous combined HRT, or sequential or cyclic HRT with >10 days of progestin per cycle, appears to decrease the incidence of endometrial cancer to that found in nonusers of HRT. The use of HRT in postmenopausal women with a uterus reduces the incidence of endometrial cancer. The duration of progestin administration should be 14 days or more per cycle based on recent epidemiologic data.