Letrozole in Preventing Breast Cancer in Postmenopausal Women Who Are at Increased Risk for Breast Cancer Due to High Breast Density

RATIONALE: Chemoprevention is the use of certain drugs to keep cancer from forming, growing, or coming back. The use of letrozole may stop cancer from forming or coming back in postmenopausal women who are at increased risk for breast cancer due to high breast density. PURPOSE: This randomized phase II trial is studying how well letrozole works in preventing breast cancer in postmenopausal women who are at increased risk for breast cancer due to high breast density.