Denosumab Treatment for a Residual Giant Cell Tumor of the Clivus: A Case Report and Review of the Literature

Background Giant cell tumors (GCTs) are a locally aggressive primary bone neoplasm of osteoclast-like cells. These lesions largely occur in the epiphyses of long bones, but there have been rare reports of occurrence in the pelvis, spine, or skull. Of those located in the skull, involvement of the clivus has been rarely reported. Case Description We present a case of an 18-year-old woman presenting with a third nerve palsy, found to have a lytic lesion of the upper clivus that was primarily treated with endoscopic endonasal resection. Her third nerve palsy resolved postoperatively, and subsequent histopathologic analysis revealed a GCT. Six-month postoperative magnetic resonance imaging (MRI) revealed progression of residual disease for which she was treated with adjuvant denosumab. This treatment resulted in a significant decrease in the tumor size. She subsequently underwent proton beam radiation. At 1-year postsurgery, the patient's MRI remained stable after completing denosumab and proton therapy. She was neurologically intact and had no issues from her treatment. Conclusions Denosumab has demonstrated anti-GCT efficacy. In combination with proton therapy, it has the potential to spare a young, vulnerable population from adverse long-term effects of traditional adjuvant radiation therapy. To our knowledge, this is the first report of the use of denosumab in the treatment of GCT of the clivus in the United States.