gms | German Medical Science

Objective: A cerebellar localization can be found in only approximately 0.4 - 3.4% of patients with glioblastomas. Therefore, tumor characteristics, survival, and the efficacy of therapies are not yet clear. The present study reports 8 patients with cerebellar glioblastoma treated in our institution over a period of 12 years.

Methods: Medical records and histology of 8 patients were analyzed retrospectively. EGFR amplification, pyrosequencing of H3F3A and BRAF, BRAF:KIAA1549 fusion and expression of IDH1(R132H) and ATRX were determined to obtain genetic characteristics of the tumors. Patients’ treatment history, including surgical interventions, radio-/chemotherapy regimens, radiological images, progression-free survival (PFS), and overall survival (OS) were reviewed.

Results: Six adult and 2 children (mean age 36.3 ± 26.4 years; range 1 to 67 years) underwent tumor resection via medial or lateral suboccipital craniotomy. Both children harbored a H3F3A K27M mutation, classifying tumors as diffuse midline glioma WHO grade IV H2-positive in accordance to the WHO 2016 classification. In one of these tumors also showed a BRAF V600E mutation. Interestingly, this child had a PFS of 64 months. Both children underwent radio-/chemotherapy. Several surgeries were required due to LCS disturbance. In the 6 adult patients, mutation of IDH1 R132H is expressed in 2 glioblastomas, indicating a relation to typical supratentorial IDH-mutant gliomas. In both cases, the patients initially had presented with such lesion, which, however, were anatomically distant to the cerebellar glioblastoma. Another patient with a cerebellar glioblastoma initially had a mesencephalic pilocytic astrocytoma. The cerebellar tumor neither revealed a BRAF:KIAA1549 fusion nor a BRAF V600E mutation. The remaining 3 patients exhibited neither clinical nor molecular characteristics that would allow an assignment to a particular entity. Mean PFS was 4.83 months. Mean follow-up time was 15.3 ± 21.9 months and median OS was 12 months in all patients.

Conclusion: Glioblastomas of the cerebellum can be found in all age groups. Our results indicate that a fraction of such tumors are presumably metastatic lesions due to tumor cell migration or cerebrospinal fluid seeding. Some tumors, however, may indicate original glioblastoma of the cerebellum. Mutation of BRAF V600E may have a stronger biological significance than H3F3A K27M alterations. In comparison to patients who had supratentorial glioblastoma, the OS of patients with cerebellar glioblastoma appears to be lower.