Prospective study on gynaecological effects of two antioestrogens tamoxifen and toremifene in postmenopausal women

To assess and compare the gynaecological consequences of the use of 2 antio estrogens we examined 167 postmenopausal breast cancer patients before and during the use of either tamoxifen (20 mg/day, n = 84) or toremifene (40 mg /day, n = 83) as an adjuvant treatment of stage II-III breast cancer. Detai led interview concerning menopausal symptoms, pelvic examination including transvaginal sonography (TVS) and collection of endometrial sample were per formed at baseline and at 6, 12, 24 and 36 months of treatment. In a subgro up of 30 women (15 using tamoxifen and 15 toremifene) pulsatility index (PI ) in an uterine artery was measured before and at 6 and 12 months of treatm ent. The mean (+/-SD) follow-up time was 2.3 +/- 0.8 years. 35% of the pati ents complained of vasomotor symptoms before the start of the trial. This r ate increased to 60.0% during the first year of the trial, being similar am ong patients using tamoxifen (57.1%) and toremifene (62.7%). Vaginal drynes s, which was present in 6.0% at baseline, increased during the use of tamox ifen (26.2%) and toremifene (24.1%). Endometrial thickness increased from b aseline (3.9 +/- 2.7 mm) to 6.8 +/- 4.2 mm at 6 months (P < 0.001), and no difference emerged between the 2 regimens in this regard. Before the start of the antioestrogen regimen, the endometrium was atrophic in 71 (75.5%) an d proliferative in 19 of 94 (20.2%) samples; 4 patients had benign endometr ial polyps. During the use of antioestrogen altogether 339 endometrial samp les were taken (159 in tamoxifen group, 180 in toremifene group). The endom etrium was proliferative more often in the tamoxifen group (47.8%) than in the toremifene group (32.2%) (P < 0.0001). 20 patients had a total of 24 po lyps (17 in tamoxifen and 9 in toremifene group, P < 0.05) during the use o f antioestrogens. One patient in the toremifene group developed endometrial adenocarcinoma at 12 months, and one patient had breast cancer metastasis on the endometrium. Tamoxifen failed to affect the PI in the uterine artery , but toremifene reduced it by 15.0% (P < 0.05) by 12 months. In conclusion , tamoxifen and toremifene cause similarly vasomotor and vaginal symptoms. Neither regimen led to the development of premalignant endometrial changes. Our data suggest that so close endometrial surveillance as used in our stu dy may not be mandatory during the first 3 years of use of antioestrogen tr eatment. (C) 2001 Cancer Research Campaign.