NCOG-50. LONG TERM-SURVIVAL OF AN ELDERLY PATIENT WITH GIANT CELL CEREBELLUM GLIOBLASTOMA (GBM)

Abstract INTRODUCTION Primary cerebellar glioblastoma (GBM) in adult is very rare and accounts for 1% of all GBM. Giant cell variant cerebellar GBM is even rarer. Because of the rarity, its molecular feature, the response to the standard treatment, and biological behavior of tumor progression are not well understood. CASE REPORT An 80 yo male presented with headache, nausea, vomiting and ataxia in 2019. Brain MRI was notable for a large enhancing cerebellar mass. Surgical resection was completed, and pathology was giant cell GBM. Molecular studies showed IDH-wildtype, CDKN2A/B copy number loss, positive TP53 G262V mutation as well as KIT and KDR amplification. The patient underwent standard 6-week concomitant temozolomide (TMZ) and radiation therapy. He only completed 3 cycles of low dose adjuvant temozolomide and two cycles of lomustine due to intolerance of both chemotherapy agents. After that the patient has been off treatment and received brain MRI surveillance over past 4 years. Two years later, his brain MRI showed new punctuate lesions in the radiation field. Suspecting the radiation necrosis; the patient underwent observation. Later, more nodular enhancing lesions developed at the outside region of the radiation field. Tumor progression was considered but the patient wished no biopsy or re-radiation. The new small nodular lesions on MRIs over past two years have behaved unusually with small fluctuations among mild progression, stabilization, or regression. His physical functions have been preserved with a Karnofsky Performance Status scale of 90% with normal cognition. DISCUSSION The patient, who is now 85 years old, has surpassed a 4.5-year survival mark, which is remarkable compared to the supratentorial and the cerebellar GBM with a few months’ survival mark in elderly patients. Our experience emphasizes the different behavior (good response) of a very rare giant cell cerebellar GBM to the standard treatment for newly diagnosed GBM.