Breast Cancer Chemoprevention by SOM230, an IGF-I Action Inhibitor: A Proof of Principle Trial

Atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH) increases breast cancer risk. In post menopausal women, SERMS are standard chemopreventive agents. The investigators have previously shown insulin-like growth factor-I (IGF-I) is required to permit estrogen (E2) and progesterone action in the mammary gland, and that a novel somatostatin analog, SOM230, that inhibits IGF-I action can prevent E2 action on the mammary gland. It reduces cell proliferation and increases apoptosis (cell death) in the rat mammary gland. This study was designed to determine whether women at high risk for breast cancer respond to SOM230 in the same way that rats do. Methods: Women with atypical ductal hyperplasia or lobular carcinoma in-situ by core biopsy were treated for 9.5 days with SOM230 (600mcg BID). Surgical excision was performed on day 10. Sections were examined before and after SOM230 treatment for cell proliferation (Ki67) and apoptosis (TUNEL). Serum IGF-I, fasting glucose, insulin, and HbA1C were measured in anticipation of changes.