Decoding Cerebellar Glioblastoma: Incidence, Distinctive Features, and Prognostic Determinants Among over 1500 Glioblastoma Patients

Introduction: Cerebellar glioblastoma (cGBM) is rare in adults, with limited data on its characteristics and outcomes compared to supratentorial glioblastoma (stGBM). Our study identifies cGBM subsets based on location and investigates their distinct clinical features and outcomes, addressing the knowledge gap in understanding cGBM.

Methods: Retrospective analysis of newly-diagnosed cGBM patients from 2004-2016 who underwent first resection at the authors’ institution. Brainstem gliomas with extension into the cerebellar peduncles were excluded.

Results: Among 1,726 GBM patients, 58 (3.3%) had cerebellar involvement. These were divided into two cohorts: (1)purely cerebellar GBMs at diagnosis (n=11, 19.0%) and (2)initially stGBM that developed cerebellar tumors (n=47, 81.0%). For cohorts 1 and 2 respectively, mean age at cGBM diagnosis was 51 vs 58.28 years (p=0.2), male distribution was 54.5% vs 56.7% (p=0.9), and mean cGBM diameter was 3.45 vs 1.76 cm (p < 0.001). Primary treatment for cohort 1 was resection alone (45.4%) or resection plus adjuvant chemoradiation (27.3%). Cohort 2 primarily received chemotherapy alone (34.04%) or chemoradiation (31.9%). Median overall survival (OS) from GBM diagnosis was similar between cohorts (13.3 vs 14.6 months, p=0.5). However, median survival following cGBM diagnosis was significantly shorter for cohort 2 (5.84 vs 13.3 months, p=0.01). Multivariate analysis identified age >50 years (HR=1.76, p< 0.001) and larger tumor size (HR=1.95, p=0.003) as independent predictors of poor survival of cGBM. Gross total resection (GTR; HR=0.58, p=0.009) and surgery plus chemoradiation (HR=0.44, p=0.002) were associated with longer survival.

Conclusion : cGBM and stGBM with cerebellar spread exhibit distinct clinical features but similar OS. While cerebellar spread in stGBM did not significantly impact OS, patients had shorter survival post-cerebellar diagnosis. Aggressive treatment, including GTR and postoperative chemoradiation, is recommended for cGBM patients for best outcomes. Future studies should focus on identifying molecular characteristics of these two distinct cGBM types to further refine treatment strategies and improve patient prognosis.