Denosumab and MRI Breast Imaging

According to the results of several studies footnoted in this protocol, there is now convincing evidence that extensive areas of radiographically-dense tissue in the breast is an independent risk factor for the development of breast cancer. Here, the investigators postulate that it is RANK ligand that mediates the association between breast density and risk of breast cancer for which progesterone is one of several factors that influence the availability of RANK ligand in mammary tissue to promote or sustain higher breast density. As such, the investigators hypothesize that inhibition of RANK ligand with the anti-RANK ligand antibody therapeutic agent denosumab will decrease breast density; a risk factor for breast cancer development. The investigators will test the primary hypothesis that RANK ligand inhibition by denosumab (Xgeva) given 120mg monthly to pre- and post-menopausal breast cancer patients will significantly decrease breast density over 6 months. Breast density will be assessed by magnetic resonance fat water imaging (MR-FW) of the breast. At the beginning of the study participants will be measured for a change in breast density by MRI between baseline 1 and baseline 2 (end of 3 months observation period). All patients will then receive 6 months of 120 mg denosumab subcutaneously every month with repeat MR imaging to obtain measurements after 6 months on denosumab. All participants will be asked to provide an optional core needle breast biopsy sample at baseline and after 6 months on denosumab.