Effect of Denosumab on Recurrent Giant Cell Reparative Granuloma of the Lumbar Spine

Design. A case of recurrent giant cell reparative granuloma (GCRG) of the lumbar spine successfully treated with denosumab is reported; a fully human monoclonal antibody against the receptor activator of nuclear factor kappa B (RANK) ligand (RANKL). Objective. To report the first case of recurrent GCRG of the lumbar spine treated with denosumab. Summary of Background Data. GCRG is a non-neoplastic osteofibrous lesion usually found in the maxilla and mandible but rarely in the spine. It is clinically distinct from giant cell tumor of bone (GCTB), although common histological characteristics such as the proliferation of spindle-shaped stromal cells and multinucleated giant cells are shared. Denosumab has recently been reported to be effective for unresectable GCTB; however, there is only one report of its effect on GCRG. Moreover, the effect of denosumab on GCRG of the spine is unknown. Methods. The clinical course, radiological features, pathology, and treatment outcome of a patient with recurrent GCRG of the lumbar spine treated with denosumab are documented. Results. Denosumab treatment was used for this patient with unresectable recurrent GCRG of the lumbar spine. Follow-up lumbar radiography showed significant bone formations in the tumor lesion after 3 months of treatment. On follow-up computerized tomography scans of the L2 and L3 vertebral lesions, the replacement of osoteolytic lesions by the formation of cortical-like bone tissue was clearly identified. Conclusion. We report the first case of recurrent GCRG of the spine successfully treated with denosumab. Treatment with denosumab induced significant bone formation in the unresectable lumbar lesion with stable clinical improvement during the 12-month follow-up period without apparent complications. Denosumab shows promise as a new alternative treatment option for osteoclastic giant cell-rich tumors, such as GCRG, especially for unresectable lesions of the spine.