Exemestane and Celecoxib in Postmenopausal Women at High Risk for Breast Cancer

Background: Evidence from adjuvant treatment trials of invasive breast cancer with aromatase inhibitors suggests that these agents are superior to tamoxifen in preventing contralateral breast cancer and are well tolerated. These agents are promising breast cancer chemopreventive agents. Data on safety and effect on surrogate biomarkers in a healthy at risk population is lacking. Objectives: Primary: -The primary objective is to evaluate the study drug effects on mammographic density after one year on treatment. Secondary: -Secondary objectives include assessing the effect of the intervention on bone mineral density, serum hormones and lipids, and breast tissue biomarkers. Eligibility: Eligible patients are postmenopausal women who meet one of the following criteria: * History of stage I or II breast cancer 2 years out from definitive therapy. * Gail model 5 year risk greater than or equal to 1.7% * History of treated ductal carcinoma in-situ (DCIS) * History of high risk lesion on breast biopsy (atypical ductal hyperplasia (ADH), atypical lobular hyperplasia (ALH), lobular carcinoma in-situ (LCIS)) * Known or suspected breast cancer 1, early onset (BRCA1) or breasts cancer 2, early onset (BRCA2) mutation * Subjects must have adequate bone mineral density by dual-emission x-ray absorptiometry (DEXA) scan in order to enroll. Design: * This is an open label study of exemestane in postmenopausal women with an elevated risk of developing invasive breast cancer. Forty five subjects will be enrolled and receive standard dose exemestane (25 mg each day (QD)), calcium and vitamin D. * Each subject will continue treatment for a total of two years. * Changes in mammographic breast density and bone mineral density will be evaluated annually which will provide long term biomarker and safety information about prevention therapy with exemestane.