OBJECTIVES: Bone metastases occur in up to 75% of patients with advanced breast cancer.  Skeletal complications of bone metastases include pathologic fracture, spinal cord compression, and surgery and radiation to bone.  In a recently completed trial of breast cancer patients with bone metastases, denosumab, a fully human monoclonal anti-RANKL antibody, was superior to zoledronic acid (ZA) in delaying/preventing skeletal related events (SRE). METHODS: Eligible patients (N=1026, denosumab; N=1020, ZA) received monthly subcutaneous denosumab 120 mg or intravenous ZA 4 mg in a double-bind, double-dummy design. Health resource utilization (HRU) data, excluding protocol-specified visits, were collected from all randomized patients monthly through end of study (median duration 17 months, both groups). RESULTS: Comparing patients who experienced any on-study SRE (n=315, denosumab; n= 372, ZA) with patients without an on-study SRE, a greater proportion reported at least one radiation oncology unit visit (22.9% vs 8.7%), clinic visit (75.5% vs 71.1%), and inpatient hospitalization (62.9% vs 48.6%).  The mean number of clinic visits and inpatient hospitalizations was also greater for patients who experienced an on-study SRE.  A between-treatment group comparison of denosumab vs ZA demonstrated that for patients with one or more clinic visits who experienced any on-study SRE, the denosumab group had 10% fewer mean clinic visits compared with the ZA group (15.5 vs 17.2 visits).  Additionally, mean radiation oncology clinic visits were decreased by 32% in the denosumab compared with the ZA group (4.2 vs 6.2 visits) and mean inpatient hospitalizations were decreased by 12% (3.7 vs 4.2 hospitalizations). CONCLUSIONS: Regardless of treatment group, patients who had an on-study SRE had greater HRU compared with patients not experiencing an on-study SRE.  In this study, among those with any on-study SRE, patients treated with denosumab had fewer clinic visits, radiation oncology unit visits, and inpatient hospitalizations compared to patients treated with zoledronic acid.