Assessment of uterus, bone, serum lipids, and hormones in postmenopausal breast cancer patients treated with TAS-108, a novel steroidal antiestrogen: Results of a randomized phase II study

1120 Background: TAS-108, a novel steroidal antiestrogen, has demonstrated a favorable safety profile, including lower agonistic activity on uterus than tamoxifen and supportive effect on bone in preclinical studies. The potential tissue-specific effect of TAS-108 was investigated in postmenopausal breast cancer patients included in a randomized phase II study. (The clinical efficacy and safety results were presented at the 31st San Antonio Breast Cancer Symposium). Methods: Postmenopausal women aged 20–80 years with hormone receptor-positive metastatic breast cancer were eligible for this study and treated with oral TAS-108 (40, 80, or 120 mg/day) once a day. Endometrial thickness (ET) was measured by ultrasonography. The change in Bone Mineral Density (BMD) at lumber spine was assessed by dual energy X-ray absorptiometry. Hormone levels, bone metabolism markers, and serum lipid parameters were also measured at regular intervals. Wilcoxon signed-rank test was used to assess the significance of changes or...