OBJECTIVES:~Determine the efficacy of exemestane in decreasing breast density at least 1 grade in postmenopausal women with increased radiological breast density at increased risk for breast cancer.~Determine whether the decrease in breast density is sustained 1 year after the cessation of this drug in these participants.~Correlate the grade of breast density with bone density at baseline and at 1 year in participants treated with this drug.~Determine the overall safety of this drug, in terms of bone and lipid metabolism and toxicity, in these participants.~Determine the menopause-specific quality of life of participants treated with this drug.~OUTLINE: This is a randomized, double-blind, placebo-controlled, multicenter study. Participants are stratified according to baseline mammographic density grade (2 vs 3 vs 4 vs 5 vs 6). Participants are randomized to 1 of 2 treatment arms.~Arm I: Participants receive oral exemestane once daily for 1 year.~Arm II: Participants receive oral placebo once daily for 1 year. In both arms, treatment continues in the absence of disease or unacceptable toxicity.~Quality of life is assessed at baseline and then at 3, 6, 9, 12, 18, and 24 months.~Participants are followed at 18 and 24 months.~PROJECTED ACCRUAL: A total of 120 participants (60 per treatment arm) will be accrued for this study.
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.