Low Dose Exemestane vs Low Dose Tamoxifen in Post-menopausal Women at High Risk for Breast Cancer.

This study compares two low-dose hormone-blocking medications — exemestane and tamoxifen — to see which is more effective at reducing the risk of developing invasive breast cancer in postmenopausal women who are at high risk due to a pre-cancerous breast condition called DCIS (ductal carcinoma in situ) or lobular neoplasia, or due to a strong family history. **You may be eligible if...** - You are postmenopausal (no periods for at least 12 months) - You have been diagnosed with DCIS, lobular neoplasia, or have a strong family history of breast cancer - For DCIS patients: you have had breast-conserving surgery with clear margins - Your estrogen receptor status meets the study's criteria **You may NOT be eligible if...** - You have invasive breast cancer - You have significant bone loss (osteoporosis) or other conditions making hormone therapy unsafe - You are premenopausal Talk to your doctor to see if this trial is right for you.