Incidence of Optic Nerve Involvement in Pediatric Intracranial Germ Cell Tumors

Abstract

Optic nerve (ON) involvement for intracranial germ cell tumors (GCT) is rare and only reported in the literature in case reports. ON involvement has important implications for radiation (RT) planning as this region may not be included in craniospinal (CSI) and whole ventricle (WV) volumes. In addition, brain MRIs may not optimally image the ON and orbital MRIs, if obtained at diagnosis, may better characterize ON involvement. We investigated the incidence of ON involvement in patients with intracranial GCTs in a large cohort of patients. All patients with intracranial pure germinoma and nongerminomatous GCTs treated at our institution with proton radiation therapy between 1998 and 2013 were included. We identified 78 patients with intracranial GCTs treated with proton radiation therapy at our institution: 45 pure germinoma and 33 nongerminomatous GCT. Of these patients, 4 (5.1%) had ON involvement based on pre-treatment MRI. Of the 4 patients with ON involvement at diagnosis, 3 had localized suprasellar tumors and 1 had disseminated disease. Median age at diagnosis was 16 years, and 3/4 patients were male. The histology was pure germinoma in 3/4 patients, and NGGCT in one patient. All were treated with induction chemotherapy for 3-6 cycles with near complete (n = 2/4) to complete (n = 2/4) response, followed by proton radiation therapy with craniospinal irradiation (n = 3/4) or whole-ventricular irradiation (n = 1/4) and involved-field radiation therapy. Optic nerve involvement meaningfully impacts radiation field planning in the treatment of intracranial GCTs. While relatively rare overall, it may be more common than previously recognized. It is important to look for ON involvement and adjust fields appropriately to ensure full radiation dose to this area of disease involvement.