Interest of Denosumab for the Treatment of Giant-cells Tumors and Aneurysmal Bone Cysts of the Spine. About Nine Cases.

STUDY DESIGN A prospective cohort study. OBJECTIVE The aim of this study was to evaluate the interest of denosumab in the treatment of spinal giant-cells tumors (GCTs) and aneurysmal bone cysts (ABCs). SUMMARY OF BACKGROUND DATA To treat GCTs and ABCs, surgical resection remains the best treatment to limit local recurrence (LR) but constitutes an aggressive treatment with potential morbidity. Denosumab, a human antibody anti-RankL, inhibiting the differentiation of osteoclasts, could be an alternative treatment to avoid aggressive surgery. METHODS Patients suffering from GCTs and ABCs of the spine were included. Patients received a monthly subcutaneous injection of denosumab (120 mg) during a minimum of 6 months either as a neoadjuvant or as an adjuvant therapy. In association with denosumab, an osteosynthesis was added in case of vertebral fracture and a laminectomy in case of spinal cord compression. Clinical and computed tomography (CT)-scan outcomes were analyzed. RESULTS Eight GCTs and one ABC were included. The mean age was 35 years (range: 22-55 yr). Five patients had neurologic deficit. All patients were operated: six osteosynthesis, one "en bloc" resection, four curettages, and two of them associated with an osteosynthesis. Average duration of denosumab therapy was 12.9 months (range: 3.2-24 months). Among them, four patients began denosumab 6 months at least before the surgery. With a mean follow-up of 19.3 months (range: 3.2-52.4 months), back pain and neurologic deficit improved for all patients. Systematic CT-scan at 6 months showed decrease of tumor size and bone consolidation. Regarding patients treated by neoadjuvant denosumab treatment, intraoperative histologic analysis showed an absence of giant cells and a maximum of 10% of alive tumor cells. CONCLUSION Denosumab allows bone formation and tumor regression with a maximum efficacy after 6 months of treatment without widely substituting surgery. Long-term results are mandatory to confirm the interest of denosumab and to evaluate LR when stopping denosumab. LEVEL OF EVIDENCE 3.