Characteristics of cerebellar glioblastomas in adults

Adult cerebellar glioblastomas (cGBM) are rare and their characteristics remain to be fully described. We analyzed the characteristics of 17 adult patients with cGBM and compared them to a series of 103 patients presenting a supra-tentorial glioblastoma (stGBM). The mean age at GBMc diagnosis was 53.4 years (range 28-77). A history of neurofibromatosis type I was noted in 3 patients. cGBM were hemispheric in 10 patients (58.8%), only vermian in 4 patients (23.5%), and both vermian and hemispheric in 3 patients (17.7%). A H3 K27M mutation was identified in 3/14 patients, a TERT promoter mutation in 3/14 patients and a methylated MGMT promoter in 3/14 patients. None of the patients (0/14) harbored an EGFR amplification, an IDH or a BRAF mutation. Association with neurofibromatosis type I and H3K27M mutations were mutually exclusive. Compared with stGBM, cGBM occurred in younger patients (53.4 vs. 63.2, p = 0.02), were more frequently associated with neurofibromatosis type I (18 vs. 1%, p = 0.009) and with a H3 K27M mutation (21 vs. 3%, p = 0.02). They also tended to have a more frequent multifocal presentation at diagnosis (21 vs. 4.3%, p = 0.06), more frequently resulted in leptomeningeal or intra-axial metastasis (44.5 vs. 5%, p = 0.002) and were associated with a shorter median overall survival (5.9 vs. 14.2 months, p = 0.004). The present study suggests that adult cGBM differ from their supra-tentorial counterpart and constitute a heterogeneous group of IDH wild-type gliomas with at least two subgroups, one associated with H3K27M mutations and the other with neurofibromatosis type I.