Denosumab for Breast Cancer With Bone Mets

Study Drug Administration: If you are found to be eligible to take part in this study, you will receive denosumab through a needle under your skin on Day 1 of each 28-day study cycle. Starting on Day 1 of week 4, you will also begin taking a hormonal drug. The study doctor will choose the hormonal drug you receive based on your previous hormonal therapy for breast cancer. The study doctor will give you instructions for taking your hormonal drug. Study Visits: On Day 1 of week 4: * You will have a physical exam * Blood (about 3 tablespoons) will be drawn for routine tests * Blood (about 5 teaspoons) will be drawn for CTC testing and to check your immune system. * Urine will be collected to test for a biomarker that is used to measure the rate of bone breakdown. * If the study doctor thinks it is needed, you will have a PET scan, a bone scan, or an MRI to check the status of the disease. On Day 1 of Cycle 2 and Cycle 3, blood (about 1 teaspoon) will be drawn for routine tests. Length of Study: You may receive the denosumab and hormonal therapy combination for up to 13 weeks. You will be taken off study if the disease gets worse or intolerable side effects occur. End of Study Visit: After your last dose of the study drug, the following tests and procedures will be performed: * You will have a physical exam. * Blood (about 3 tablespoons) will be drawn for routine tests. * Blood (about 5 teaspoons) will be drawn for CTC testing and to check your immune system. * Urine will be collected to test for a biomarker that is used to measure the rate of bone breakdown. * If the study doctor thinks it is needed, you will have a PET scan, a bone scan, or an MRI to check the status of the disease.