Additional Study Information: The purpose of this study is to find out whether denosumab can decrease or prevent the risk of developing breast cancer in women carrying the BRCA1 mutation, looking at whether denosumab can decrease the risk of developing ovarian cancer or other types of cancer in women carrying the BRCA1 mutation, and studying the drugs safety and its effect on bone health. The study team also will be monitoring for any potential side effects the drug might cause. Participants in this study will randomly be assigned to receive denosumab or a placebo. A placebo is a substance that does not contain any study drug and has no therapeutic value. Placebos are used in studies to help the study team determine if any progress occurs due to the study treatment or due to another outside factor that is not being studied in this research. A computer will randomly choose whether you are assigned to the denosumab group or the placebo group. Neither you nor your study doctor will know whether you are receiving denosumab or a placebo.