Background: Bone is a common site of distant recurrence in women with early-stage breast cancer, and represents approximately 40% of all first recurrences. Tumor cells in bone release growth factors and cytokines that stimulate osteoclast-mediated bone resorption through the RANK ligand (RANKL) pathway. In preclinical studies, RANKL inhibition significantly delays skeletal tumor formation, reduces skeletal tumor burden, and prolongs survival of tumor-bearing mice. Denosumab is a fully human monoclonal antibody that binds to RANKL with high affinity and specificity. It is approved for the prevention of skeletal-related events in patients with established bone metastases from a variety of solid tumors. The purpose of the D-CARE trial is to evaluate the ability of denosumab to prolong bone metastasis-free survival (BMFS) and disease-free survival (DFS) in the adjuvant breast cancer setting. Methods: Approximately 4,500 women with stage II or III breast cancer, at high risk for recurrence and with known hormone and HER-2 receptor status, are eligible. Standard-of-care adjuvant or neoadjuvant chemo-, endocrine, or HER-2 targeted therapy, alone or in combination must be planned. Exclusion criteria include: a prior history of breast cancer (except DCIS or LCIS) or distant metastasis, oral bisphosphonate (BP) use within 1 year of randomization or any intravenous BP use. Patients are randomized 1:1 to receive denosumab 120 mg or placebo subcutaneously monthly for 6 months, then every 3 months for a total of 5 years of treatment. All patients receive vitamin D (≥ 400 IU) and calcium (≥ 500 mg) supplements. Primary endpoint of this event-driven trial is BMFS. Secondary endpoints include DFS and overall survival. Safety, quality of life assessments, breast density, and biomarkers are additional endpoints. The trial, sponsored by Amgen Inc. and registered with the ClinicalTrials.gov identifier NCT01077154, began enrolling patients in June 2010 and is expected to complete in October 2016. Paul Goss and Dianne Finkelstein supported in part by the Avon Foundation New York.