This case report is a 30 years old male. He visited a hospital with 10 months history of low back pain and radiated to right leg. 1 months before visited he had a progressive low back pain, weakness and numbness at posterolateral on the right foot. He had no history a change of bowel habits. MRI shown a huge sacrum mass size 8.6×9.3×9.3 cm extended to right psoas muscle and spinal canal. In October 2017 He was referred to Ramathibodi hospital for tissue biopsy and treatment. CT before biopsy revealed a progressive mass at a middle and right-side sacrum from 8.6×9.3×9.3 cm to 10.9×11×10.2 cm in size. Before CT-guided biopsy at sacral mass, Blood biochemistry analysis revealed that the alkaline phosphatase and other was normal. The biopsy was done and histopathology shown giant cell tumor. Neurosurgeon and radiologist evaluated the lesion and they concluded that no role of surgery and embolization at that time because the tumor was a large and hypervascular tumor. So the denosumab was initiated. The patient received denosumab 120 mg with loading dose in day 8 and 15 in 1 cycle. He received monthly denosumab 120 mg from November 2017 to March 2018. His symptoms about pain were resolution and right foot weakness improving the motor power of extensor hallucis longus from grade 2 to grade 4 in 5 months. Following MRI revealed the tumor no significant change in size (9.1×11×11 cm) but the tumor had a lessor cellularity and increased fibrous portions. We continue a denosumab until now and do next evaluated MRI in August 2018. We plan to evaluate about embolization and surgery after next MRI scan.
Giant cell tumor of the bone is an aggressive benign bone tumor. It accounts for approximately about 20% of all benign bone tumors in the adult. Usually, tumors occur at the end of the long bone. Only 6% occur in the sacrum. Surgery is the mainstay of treatment giant cell tumor but a difficulty in the scral area. No standard of chemotherapy. In the present, we know about Giant cell express RANKL (receptor activator of nuclear factor κB ligand) and denosumab is monoclonal antibody and highly specific to RANKL. The patient response to denosumab. He has no symptom of pain and improving right foot weakness.