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

Inclusion Criteria: * Women with a confirmed deleterious or likely deleterious BRCA 1 germline mutation (variant class 4 or 5) * Age \>= 25 years and =\< 55 years at randomization * No evidence of breast cancer by MRI or mammography (MG) and clinical breast examination within the last 6 months prior to randomization * No clinical evidence of ovarian cancer at randomization * Negative pregnancy test at randomization for women of childbearing potential * No preventive breast surgery planned at time of randomization * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Written informed consent before any study-specific procedure is performed Exclusion Criteria: * Prior bilateral mastectomy * History of ovarian cancer (including fallopian and peritoneal cancer) * History of breast cancer * History of invasive cancer except for basal cell or squamous cell skin cancer or carcinoma in situ of the cervix, stage 1 papillary or follicular thyroid cancer, atypical hyperplasia or LCIS (lobular carcinoma in situ) * Pregnant or lactating women (within the last 2 months prior to randomization) * Unwillingness to use highly effective contraception method during and within at least 5 months after cessation of denosumab/placebo therapy in women of childbearing potential. (Note: Women of childbearing potential should be monitored for pregnancy prior to each denosumab/placebo injection) * Clinically relevant hypocalcemia (history and current condition), or serum calcium \…