Tamoxifen in Preventing Breast Cancer in Women at Increased Risk for Breast Cancer

RATIONALE: Chemoprevention therapy is the use of certain drugs to try to prevent the development or recurrence of cancer. The use of tamoxifen may be effective in preventing breast cancer. PURPOSE: This randomized phase II trial is studying tamoxifen to see how well it works compared to placebo in preventing breast cancer in women who are at increased risk for the disease.