BT-09 CLINICAL AND MOLECULAR GENETIC FEATURE OF CEREBELLAR GLIOBLASTOMA

INTRODUCTION: Cerebellar glioblastoma (cGBM) is extremely rare, accounting for 0.7–0.9% of all gliomas. Few studies have reported on clinical course, histopathology, and prognosis. In this report, we discussed cases which were diagnosed as cGBM, and were treated in our institute. MATERIALS AND METHODS: We retrospectively analyzed 9 cGBMs (age ranged 41 to 85 years, median 69), operated at our institute after 2010 January, and evaluated their <MGMT> promoter methylation, <IDH1> mutation, and Copy Number Variation status detected by methylation-specific PCR (MSP), DNA sequencing or immunohistochemistry, and Multiplex Ligation-dependent Probe Amplification (MLPA), respectively. RESULTS: All patients underwent resection; 3 gross total resections (GTRs, 33%), 2 subtotal resections, 4 partial resections, with relatively low achievement of GTR. The tumor location predominated in the cerebellar hemisphere (7 patients, 78%) over vermis (2). One patient had brain stem invasion. After surgery, 8 patients received temozolomide (TMZ) and radiotherapy (RT), while did only one RT alone. After recurrence, three patients were treated with bevacizumab monotherapy, and other three received either TMZ and RT, TMZ and ACNU, or TMZ monotherapy. The median progression-free survival (PFS) was 12.0 months, and the median overall survival (OS) was 17.1 months. Five patients (56%) were <MGMT> methylated, whereas all were <IDH1>wild-type. <PTEN> deletion was negative in all patients. <EGFR> amplification and combined <PDGFR> amplification and <CDKN2A> deletion were found in one patient each. DISCUSSION: Despite the lower rate of GTR, there was a tendency of longer PFS compared to supratentorial GBM (sGBM). The clinical course after recurrence was unfavorable, and OS thereafter was similar to that of sGBM. cGBMs appeared to lack the typical genetic mutations occurred in sGBM, suggesting that cGBMs might be stimulated with different regulatory cellular signals.