Letrozole in Preventing Breast Cancer in Healthy Postmenopausal Women at High Risk for Breast Cancer

PRIMARY OBJECTIVES: I. Compare the effect of lower and intermittent doses of letrozole to standard letrozole therapy on estrogen suppression in postmenopausal women at high risk for developing breast cancer. SECONDARY OBJECTIVES: I. Comparison of the effect of lower and intermittent doses of letrozole to standard therapy on signs and symptoms of estrogen deficiency, including menopausal symptoms, serum lipid profile, and serum marker of bone turnover. II. Comparison of the effect of lower and intermittent doses of letrozole to standard therapy on nuclear chromatin abnormality of breast epithelial cells collected by random periareolar fine needle aspiration (RPFNA). TERTIARY OBJECTIVES: I. Determine the prevalence of breast cancer stem cells in the fine needle breast aspirates and explore the potential intervention effect on the prevalence of breast cancer stem cells. OUTLINE: Patients are randomized to 1 of 4 treatment arms. ARM I: Patients receive 2.5 mg of letrozole orally (PO) thrice weekly for 6 months. ARM II: Patients receive 1.0 mg of letrozole PO thrice weekly for 6 months. ARM III: Patients receive 0.25 mg of letrozole PO thrice weekly for 6 months. ARM IV: Patients receive 2.5 mg of letrozole PO once daily for 6 months. After completion of study treatment, patients are followed up at week 30.