Reduction In Ki-67 In Benign Breast Tissue Of High-Risk Premenopausal Women With The Serm Acolbifene

520 Background: Selective Estrogen Receptor Modulators (SERMs) are approved for reduction of risk for breast cancer; however, uptake and use is limited. We conducted a pilot study of a 4th generation SERM to determine tolerability and effect on tissue biomarkers in healthy women at high risk for development of breast cancer. Methods: Premenopausal women at elevated risk for breast cancer were screened by random periareolar fine needle aspiration (RPFNA) performed during the follicular phase of the menstrual cycle. Women were eligible if breast epithelial cells exhibited evidence of cytologic hyperplasia with or without atypia, as well as Ki-67 ≥2% by immunocytochemistry. Following 6-8 months of open-label acolbifene (20 mg/d), the RPFNA was repeated. The primary endpoint was modulation of the proportion of cells that expressed Ki-67. Body composition (DEXA), pelvic sonography, mammographic breast density, and serum levels of IGF-1/IGFBP3 and several bioavailable hormones were assessed pre and post interve...