Follicle-stimulating hormone and estradiol levels in Japanese Women treated with toremifene and anastrozole for two years-A retrospective analysis of data from a prospective randomized trial

The criteria for biological postmenopause have not been clearly defined, although determining the menopausal status is crucial for selecting agents for adjuvant endocrine therapy for patients with breast cancer. The long-term effects of adjuvant toremifene (TOR) and anastrozole (ANA) on serum follicle-stimulating hormone (FSH) and estradiol (E2) levels in Japanese women were examined using data from a prospective randomized study that mainly studied serum lipids and bone metabolism for 2 years. The study medications were administered orally daily at 40 mg and 1 mg for TOR and ANA, respectively. Sixty-nine patients were randomly assigned to the TOR group (n=36) or ANA group (n=33). FSH and E2 levels were measured using chemiluminescent immunoassay. The mean ages of the patients in the TOR and ANA groups were 62.5 and 60.0 years, respectively. None of the patients experienced menstruation during the course of the study. The baseline serum FSH level in the TOR group (69.6mlU/mL) decreased to 59.2%, 54.6%, and 50.0% at 6, 12, and 24 months, respectively, after therapy commencement. The FSH levels ranged from 8.6 to 68.1 mIU/mL and were<20 mIU/mL in 2 patients (9.5%; 8.6 and 14.4 mIU/mL). The serum FSH levels in the ANA group did not change markedly over 24 months. The baseline serum E2 level in the ANA group (11.6 pg/mL) decreased to 72.4%, 70.7%, and 61.2% at 6, 12, and 24months, respectively, after therapy commencement. The serum E2 level in the TOR group did not change markedly over 24 months. When switching to other endocrine agents as adjuvant therapy for patients with breast cancer treated with TOR, the serum FSH level decreased to half of the preinitiation level, and one-tenth of the FSH levels was<20 mIU/mL, while the postmenopausal serum E2 level was maintained.