Toremifene as a substitute for adjuvant tamoxifen in breast cancer patients

Background: Toremifene is a new antiestrogen, which in nonclinical studies appears less carcinogenic than tamoxifen. Clinical trials of adjuvant toremifene vs, tamoxifen in breast cancer patients ave ongoing. This study aimed to evaluate the short-term effects of changing from adjuvant tamoxifen to toremifene. Patients and Methods: Twenty postmenopausal breast cancer patients receiving adjuvant tamoxifen, 20 mg/day, were switched to toremifene 60 mg/day. The effects on the uterus were evaluated prospectively by transvaginal ultrasound; tolerability was assessed clinically. Results: In 14 patients who had uterine abnormalities (endometrial thickening or polyps) under tamoxifen, no significant changes occurred during a median of 18 months (range 7-24) of toremifene treatment. Out of six patients who had entered the study due to intolerance to tamoxifen, however; 3 tolerated toremifene well. Conclusion: Toremifene does not modify previous uterine changes induced by tamoxifen. For some patients who do not tolerate tamoxifen, however, switching to toremifene may allow the continuation of adjuvant antiestrogenic therapy.