INNV-65. Long term survival of an elderly patient with giant cell cerebellum glioblastoma (GBM) on long term intravitreal injections of bevacizumab, possibly stabilizing cerebellum enhancing lesions

INTRODUCTION Giant cell variant cerebellar GBM is extremely rare. its response to the standard chemoradiation therapy, and low dose bevacizumab are not well understood. CASE REPORT The patient is an 86-year-old male who was found a left side large enhancing cerebellar cystic mass six years ago in 2019 and pathology confirmed giant cell GBM with IDH-wildtype, CDKN2A/B copy number loss, and positive TP53 G262V mutation. The patient underwent standard temozolomide (TMZ) and radiation, but his low dose adjuvant chemotherapy was discontinued after 5 cycles because of intolerance. The patient was off treatment since 5/2020. Two years later, his brain MRI showed new punctuate lesions at cerebellum. Suspecting radiation necrosis. Later multiple nodular enhancing lesions developed on the left side cerebellum borderline to the radiation field. Tumor progression was considered but the patient was doing well and decided no intervention. The multiple nodular enhancing lesions on MRIs have behaved unusually with fluctuations among mild progression, stabilization, or regression. After careful investigation, we noticed the patient was on intravitreal injection of bevacizumab (1.25 mg/0.05 ml) every 3 months since 2022 for his macular degeneration. The fluctuating size and enhancement of cerebellum enhancing lesions seem to be related to the time of intravitreal injections of bevacizumab. While the patient held on the injection due to traveling in 2023, his cerebellum lesions progressed. Resuming intravitreal injections of bevacizumab, the multiple enhancing lesions improved and stabilized again. DISCUSSION The 86 years old male with a very rare giant cell cerebellum GBM, has surpassed a 5.5-year survival mark after standard therapy. Interestingly, his long-term intravitreal injections of bevacizumab appear to stabilize his recurrent cerebellar enhancing lesions even though the lesions could be tumor recurrence or radiation effect. The response demonstrates the minimal dose of bevacizumab might help improve or stabilize brain tumor enhancement or radiation necrosis.