Abstract PO-099: Short-term outcomes of an extended endoscopic endonasal resection of a clival giant cell tumor with adjuvant RANK-L inhibitor therapy: Case report

Abstract Background Clival giant cell tumors (GiCT) are rare neoplasms that commonly target the epiphysis. Recently, skull base GiCTs have been reported, predominantly in the sphenoid and temporal bones. Although typically benign, GiCTs of the skull-base can cause neurologic deficits due to compression of cranial nerves or intracranial contents. The efficacy of adjuvant chemotherapy in treating GiCTs is not known. One potential treatment option neoplastic mononuclear stromal cells in GiCTs express NF-κB ligands (RANK-L), which can be therapeutically targeted with Denosumab, a monoclonal antibody against RANK-L. Here, we describe the case of a GiCT invasive to the clivus, an extended endoscopic endonasal resection of the tumor, and management of the lesion with Denosumab. Methods A retrospective chart review was performed on the patient of interest. Magnetic resonance imaging (MRI) and computed tomography (CT) scans were used to assess disease growth and response to surgical and therapeutic intervention. Case presentation A previously healthy seventeen-year-old female presented with headaches and numbness of the left V2 and V3. A diagnosis of a clival giant cell tumor was confirmed with strict pathologic, radiographic, and clinical correlation. She was found to have a clival mass extending into the sphenoid sinus. Surgical excision was performed by both the otolaryngology and neurosurgery departments at a single institution. She underwent an extended endoscopic endonasal resection of the clival mass. Following surgery, the numbness on the left V2 and V3 distribution improved. She occasionally reported bilateral V3 distribution symptoms without definite anatomic correlates for right sided complaints. Due to the presence of residual tumor, we recommended adjunctive medical therapy. We performed adjunctive medical therapy with Denosumab, a RANKL inhibitor. Discussion When complete surgical excision with negative margins is not feasible in lesions of the skull base, adjuvant treatment is commonly required to achieve local disease control. Our case demonstrates the efficacy of a combined approach where surgery is used to achieve a histologic diagnosis, decompression and evaluate for respectability. Adjuvant medical therapy using RANKL inhibitors is a promising approach that may be effective to achieve lifelong disease control but requires continued maintenance on therapy. Citation Format: Myra A. Zaheer, Abhisri Ramesh, Aadit P. Mehta, Adriana S. Fonseca, Daniel A. Donoho. Short-term outcomes of an extended endoscopic endonasal resection of a clival giant cell tumor with adjuvant RANK-L inhibitor therapy: Case report [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-099.

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