N28The use of denosumab in treating bone metastases from breast and prostate cancer: a Single- Institution Experience

Background: Denosumab (DEN), a human monoclonal antibody resembling natural IgG2 immunoglobulin, has antiresorptive activity and is distinguished from other antiresorptive drugs. It mimics osteoprotegerin (OPG) that binds to receptor-activator natural Killer-ligand (RANK-L) not allowing RANK-L to bind with RANK receptor. It inhibitis osteoclast differentiation, activation and survival exerting primarily antiresorptive action. In phase III studies denosumab was superior to zoledronic acid in reducing skeletal-related events (radiation to bone, pathologic fracture, surgery to bone, or spinal cord compression) in metastatic breast and prostate cancer (PC) patients (pts). Patients and methods: The purpose of this study was to evaluate the toxicity profile and activity of denosumab in bone metastatic prostate and breast cancer (BC) pts. DEN was administered as a single sub-cutaneous dose of 120 mg repeated each four weeks. Every pts received calcium/vitamin D integration. Results: From December 2013 to February 2015 we treated 32 pts. 24 pts (75%) had a diagnosis of BC and 8 pts (25%) had a PC. Median age was 55 years (range 30-80). 27 pts (83,5%) had a performance status (PS) of 0 and 5 pts (16,5%) were in PS1. 23 pts (71,8%) received at least 1 line of chemotherapy for metastatic disease (MD) and 28 pts (87,5) a median of 1 line of hormanal therapy (range 1-3). All 32 pts had a MD to bone with a median number of metastatic sites of 2 (range 1-4). Pts received a median number of administrations of 8 (range 1-16). For 24 pts (75%) treatment with DEN is still ongoing. We observed 3 (9,2%) Grade 1 (G1) ipocalcemia and 1 (3,1%) renal ipofuncion requiring treatment discontinuation. We interrupted treatment in 1 pt (3,1%) for pathologic fracture. Any G2-4 toxicity was observed. Conclusions: Treatment with DEN showed in our series a good activity and safety profile when administered a calcium – vitamin D implementation.