Treatment of a skull-base giant cell tumor with endoscopic endonasal resection and denosumab: case report

A 34-year-old man with a 1-week history of diplopia was referred to the authors' hospital. Neurological examination revealed left abducens nerve palsy. Computed tomography showed a lesion in the left sphenoid sinus involving the medial wall of the left internal carotid artery (ICA) and osteolytic change at the clivus bordering the lesion. Magnetic resonance imaging demonstrated an extensive soft-tissue mass occupying the left sphenoid sinus. Surgical intervention by the endoscopic transnasal method allowed most of the lesion to be removed. Only the portion attached to the medial wall of the ICA was not removed. Postoperatively, the lesion was diagnosed as a giant cell tumor (GCT) and the patient received 120 mg of subcutaneous denosumab every 4 weeks, with additional doses on Days 8 and 15 during the first month of therapy. MRI a week after starting denosumab revealed shrinkage of the initially fast-growing residual tumor. The patient was discharged upon completion of the third denosumab administration. GCT is an aggressive stromal tumor developing mainly in young adults. Complete resection is recommended for GCT in the literature. However, size and location of the CGT often limit this approach. Various adjuvant treatments for skull base GCTs have been reported, including radiation and chemotherapy. However, the roles of adjuvant therapies have yet to be clearly defined. Denosumab, a monoclonal antibody, was recently approved for GCT in several countries. Denosumab may permit less invasive treatments for patients with GCTs while avoiding deleterious outcomes, and may also limit disease progression and recurrence.