Comparison between the Effects of Tamoxifen and Toremifene on the Uterus in Postmenopausal Breast Cancer Patients

Abstract Antiestrogens have been widely used in the treatment of breast cancer patients. We wanted to compare the uteral and vaginal effects of tamoxifen to those of toremifene. Thirty-one gynecologically asymptomatic postmenopausal breast cancer patients with an intact uterus were randomized to receive 20 mg of tamoxifen ( N = 16) or 60 mg of toremifene ( N = 15) as an adjuvant treatment. Gynecological examination with vaginal ultrasonography, Pap smear, endometrial biopsy, hysteroscopy, and curettage was performed before the treatment, and at 6 and 12 months of treatment. Endometrial thickness was found to increase significantly during the treatment to the same extent in both groups. Proliferation or other estrogenic effects in the endometrium were observed in 8 of 14 patients in the tamoxifen group and in 3 of 10 patients in the toremifene group. Three polyps occurred and previously present uterine fibroids increased in size in 3 of 10 patients during the study. Estrogenic changes in Pap smear were observed in all patients. There was no significant difference between tamoxifen and toremifene in any of the parameters investigated. Our results suggest that tamoxifen and toremifene produce comparable estrogenic effects in the uterus and vagina.