Uterine effects of 3-year raloxifene therapy in postmenopausal women younger than age 60

Objective: To assess the uterine effects of 3 years of therapy with raloxifene in healthy, postmenopausal women under age 60. Methods: Integrated data from two identically designed, randomized, double-masked, placebo-controlled clinical trials were analyzed. Nine hundred sixty-nine healthy women with uteri (ages 45 through 60, 2 to 8 years postmenopausal) were assigned randomly to raloxifene 30, 60, or 150 mg per day, or an identical placebo for 3 years. Endometral thickness was evaluated with transvaginal ultrasonography every 6 months for 2 years and again after 3 years. Further uterine evaluation, including endometrial sampling if necessary, was initiated for vaginal bleeding or findings of endometrial thickness greater than 5 mm. Results: Endometrial thickness was unchanged by raloxifene and not significantly different from placebo at any time. One hundred seventy-two women had at least one episode of endometrial thickness greater than 5 mm or vaginal bleeding distributed equally among all groups. A total of 102 (10.5%) women underwent endometrial sampling at least once: 15 (1.5%) for vaginal bleeding, 78 (8.0%) for endometrial thickness greater than 5 mm, and nine (0.9%) for other reasons. There were no significant treatment differences in the proportion of women sampled, in the clinical findings, or in the histologic diagnoses. Conclusion: Raloxifene given to healthy postmenopausal women at doses from 30 to 150 mg per day does not stimulate uterine growth and does not cause vaginal bleeding spotting, or discharge through 3 years of therapy. Thus, any bleeding during therapy should be deemed unexpected and prompt a clinical evaluation. (Obstet Gynecol 2000;95:104-10. (C) 2000 by The American College of Obstetricians and Gynecologists.).