Exemestane in Reducing Breast Density in Postmenopausal Women at Risk for Breast Cancer

RATIONALE: High estrogen levels may be associated with dense breast tissue and an increased risk of developing breast cancer. Exemestane may be effective in preventing the development of breast cancer by decreasing estrogen levels and reducing breast density. PURPOSE: Randomized clinical trial to study the effectiveness of exemestane in preventing the development of breast cancer by decreasing estrogen levels and reducing breast density in postmenopausal women who are at increased risk for breast cancer.