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

DISEASE CHARACTERISTICS: At increased risk for the development or recurrence of breast cancer, as defined by 1 of the following: Baseline mammogram indicating mammographic density occupying ≥ 25% (grade 4/6, 5/6, or 6/6) of the breast tissue No suspicion of breast cancer, unless subsequently ruled out Prior ductal carcinoma in situ (DCIS) Untreated disease OR > 6 months since completion of adjuvant endocrine therapy Receptor status of lesion is not required Prior invasive breast cancer Breast cancer must have been surgically removed at time of original diagnosis with no evidence of metastases No clinical evidence of breast cancer Acceptable quality dual-energy x-ray absorptiometry (DEXA) of the L2-L4 postero-anterior (PA) spine and hip performed within past 6 months Bone mass density T-score of either PA spine or hip must be ≥ 2.0 SD below the mean peak bone mass in young normal woman Stable chronic leukemia allowed Hormone receptor status: Hormone receptor-negative, -positive, or -equivocal tumor PATIENT CHARACTERISTICS: Age Postmenopausal Sex Female Menopausal status Postmenopausal, as defined by 1 of the following: Over 55 years of age with spontaneous cessation of menses for ≥ 1 year 55 years of age and under with spontaneous cessation of menses for ≤ 1 year, but amenorrheic (e.g., spontaneous or secondary to hysterectomy) AND follicle-stimulating hormone level > 34.4 IU/L Bilateral oophorectomy Performance status Not specified Life expectancy Not specified Hematopoietic Not specified Hepatic Not specified Renal Not specified Cardiovascular No recent unstable myocardial infarction No prior stroke No high blood pressure No other uncontrolled cardiovascular disease Other Other prior malignancies without metastatic disease allowed Willing and able to complete quality of life questionnaires in either English or French No uncontrolled metabolic or endocrine disease No malabsorption syndrome PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent immunotherapy Chemotherapy No concurrent chemotherapy Endocrine therapy See Disease Characteristics At least 3 months since prior and no concurrent hormone replacement therapy or raloxifene At least 6 months since prior tamoxifen No concurrent steroid therapy No concurrent selective estrogen-receptor modulators No other concurrent endocrine or hormonal therapy Radiotherapy Not specified Surgery See Disease Characteristics