Genistein in Preventing Breast Cancer in Women at High Risk for Breast Cancer

PRIMARY OBJECTIVE: I. Determine the effect of genistein on the proliferation of breast epithelial cells obtained by fine needle aspiration (FNA), as measured by Ki-67 labeling index, in women who are at high risk for breast cancer. SECONDARY OBJECTIVE: I. Determine the effect of this drug on cellular and molecular parameters using epithelial cells obtained by FNA, nipple aspirate fluid, and blood from these patients. OUTLINE: This is a randomized, double-blind, placebo-controlled study. Patients are stratified according to menopausal status (premenopausal vs postmenopausal) and history of breast cancer (no history of breast cancer vs history of estrogen receptor \[ER\] positive breast cancer vs history of ER negative breast cancer). Patients are randomized to 1 of 2 treatment arms. ARM I: Patients receive oral genistein once daily. ARM II: Patients receive oral placebo once daily. In both arms, treatment continues for up to 6 months in the absence of unacceptable toxicity. After completion of study treatment, patients are followed at 30-37 days.