Studying the Effect of Denosumab on Preventing Breast Cancer in Women With a BRCA1 Germline Mutation

PRIMARY OBJECTIVE: I. To evaluate the reduction in the risk of any breast cancer (invasive or ductal carcinoma in situ \[DCIS\]) in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. SECONDARY OBJECTIVES: I. To determine the reduction in the risk of invasive breast cancer in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. II. To determine the reduction in the risk of invasive triple negative breast cancer (TNBC) in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. III. To determine the reduction in risk of ovarian, fallopian and peritoneal cancers (in women who have not undergone prophylactic bilateral salpingo-oophorectomy \[PBSO\]) in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. IV. To determine the reduction in risk of other (i.e. non-breast and nonovarian) malignancies, including those known to be associated with BRCA1 germline mutations in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. V. To determine the reduction in the risk of clinical fractures in pre- and postmenopausal women with germline BRCA1 mutation who are treated with denosumab compared to placebo. VI. To compare rates of breast biopsies and rate of benign breast lesions in women with germline BRCA1 mutation who are treated with denosumab compared to placebo. OUTLINE: Patients are randomized to 1 of 2 arms. ARM A: Patients receive denosumab subcutaneously (SC) every 6 months (q6m) for up to 5 years in the absence of the development of breast cancer or unacceptable toxicity. ARM B: Patients receive placebo SC q6m for up to 5 years in the absence of the development of breast cancer. After completion of study treatment, patients are followed up every 12 months for 5 years.