H3K27M mutation in adult cerebellar glioblastoma

A common tumour in a rare location: a single centre case series of cerebellar glioblastoma

Although glioblastoma is the commonest primary brain tumour in adults, its location in the cerebellum is extremely rare. We present thirteen cases (3 female, 10 male; median age at presentation 56 [age range 21-77]) of surgically managed, histologically confirmed, primary cerebellar glioblastoma (cGB) over a 17 year period (2005-2022). Pre-operative radiological diagnosis was challenging given cGB rarity, although MRI demonstrated ring enhancement in all cases. Surgical management included posterior fossa craniectomy and debulking in 11 cases and burr hole biopsy in two. CSF diversion was necessary in four cases. No evidence of IDH or ATRX gene mutations was found when tested. Survival ranged from 1 to 22 months after diagnosis (mean 10.9 months). We also seek to understand why glioblastoma is rare in this location and discuss potential reasons for this. We hypothesise that increasing anatomical distance from germinal regions and decreased local endogenous neural stem cell activity (which has been associated with glioblastoma) may explain why glioblastoma is rare in the cerebellum. We hereby seek to add to the limited literature on cGB as this is the largest UK cGB series to date.

Assessing the predictability of the H3K27M status in diffuse glioma patients using frequency importance analysis on chemical exchange saturation transfer MRI

BACKGROUND AND OBJECTIVES

In diffuse glioma patients, Lys-27-Met mutations in histone 3 genes (H3K27M) are associated with an aggravated prognosis and further decreased overall survival. By using frequency importance analysis on chemical exchange saturation transfer (CEST) MRI, this study aimed to assess the predictability of the H3K27M status in diffuse glioma patients.

METHODS

Twenty-two patients diagnosed with diffuse glioma, with a known H3K27M status, were included in the present study. All patients underwent CEST MRI scans. The previously proposed frequency importance analysis was performed to determine the relative contribution of the amide and aliphatic protons for the differentiation between normal tissues and tumors. For this comparison, the conventional MTRasym analysis of amide protons at 3.5 ppm, i.e., the amide proton transfer-weighted (APTw) signal, was employed. Statistical analysis was performed using the Mann-Whitney U test, and the receiver operating characteristic (ROC) and area under the curve (AUC) analyses.

RESULTS

The mean and 90th percentile of the ΔAPTw intensities, amide and aliphatic frequency importance values revealed statistically significant differences between the wildtype and the H3K27M-altered patient groups (p < 0.05). For the prediction of the H3K27M status, amide frequency importance achieved highest AUCs of 0.97, with a specificity of 0.93. In contrast, the ΔAPTw intensities and aliphatic frequency importance showed relatively lower AUCs (<0.35) in predicting the H3K27M status.

CONCLUSIONS

Amide frequency importance exhibited satisfactory performance in the prediction of the H3K27M status. As such, it may be considered as a non-invasive MRI biomarker for the diagnosis of diffuse gliomas.

Metabolic Rewiring in Glioblastoma Cancer: EGFR, IDH and Beyond

Glioblastoma multiforme (GBM), a highly invasive and incurable tumor, is the humans’ foremost, commonest, and deadliest brain cancer. As in other cancers, distinct combinations of genetic alterations (GA) in GBM induce a diversity of metabolic phenotypes resulting in enhanced malignancy and altered sensitivity to current therapies. Furthermore, GA as a hallmark of cancer, dysregulated cell metabolism in GBM has been recently linked to the acquired GA. Indeed, Numerous point mutations and copy number variations have been shown to drive glioma cells’ metabolic state, affecting tumor growth and patient outcomes. Among the most common, IDH mutations, EGFR amplification, mutation, PTEN loss, and MGMT promoter mutation have emerged as key patterns associated with upregulated glycolysis and OXPHOS glutamine addiction and altered lipid metabolism in GBM. Therefore, current Advances in cancer genetic and metabolic profiling have yielded mechanistic insights into the metabolism rewiring of GBM and provided potential avenues for improved therapeutic modalities. Accordingly, actionable metabolic dependencies are currently used to design new treatments for patients with glioblastoma. Herein, we capture the current knowledge of genetic alterations in GBM, provide a detailed understanding of the alterations in metabolic pathways, and discuss their relevance in GBM therapy.

Histone-mutant glioma presenting as diffuse leptomeningeal disease

Glioblastoma multiforme is the most common malignant primary brain tumor in adults. Histone H3 mutations have been identified in pediatric and adult gliomas, with H3K27M mutations typically associated with a posterior fossa midline tumor location and poor prognosis. Leptomeningeal disease is a known complication of histone-mutant glioma, but uncommon at the time of initial diagnosis. We describe a case of glioblastoma with H3K27M mutation that initially presented with progressive vision loss due to diffuse leptomeningeal disease in the absence of a mass lesion other than a small cerebellar area of enhancement and with cerebrospinal fluid cytology negative for malignant cells on two occasions, highlighting the importance of including primary CNS malignancies in the differential of diffuse radiographic leptomeningeal enhancement.

Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor in adults. Histones are molecules around which DNA winds. GBM and other gliomas sometimes have genetic alterations called mutations in histone genes. Of these, a specific alteration in histone 3 called H3K27M has been described in a variety of primary brain tumors. In adult gliomas, the H3K27M mutation is typically associated with tumors located within the brainstem or other structures in the midline of the central nervous system and a poor prognosis. Although previously reported, involvement of the leptomeninges (the thin membranes covering the brain and spinal cord) is uncommon at the time of initial diagnosis of gliomas harboring H3K27M mutations. We describe a case of GBM that initially presented with vision loss due to diffuse leptomeningeal involvement. Imaging and laboratory studies, including two cerebrospinal fluid analyses by lumbar puncture, did not establish a diagnosis. Brain biopsy confirmed the presence of a tumor, and genetic testing performed on the tumor tissue identified the histone mutation. This case highlights the importance of including primary central nervous system malignancies as a possible diagnosis when there is diffuse radiographic leptomeningeal enhancement.

Diffuse Gliomas of the Brainstem and Cerebellum in Adults Show Molecular Heterogeneity

Posterior fossa (PF) diffuse gliomas in pediatric patients frequently harbor the H3 K27M mutation. Among adults, PF diffuse gliomas are rare, with limited data regarding molecular features and clinical outcomes. We identified 28 adult PF diffuse glioma patients (17 males; median: 50 y, range: 19 to 78 y), with surgery performed at our institution (13 brainstem; 15 cerebellum). Histologic subtypes included anaplastic astrocytoma (n=21), glioblastoma (n=6), and diffuse astrocytoma (n=1). Immunohistochemistry was performed for H3 K27M (n=26), IDH1-R132H (n=28), and ATRX (n=28). A 150-gene neuro-oncology-targeted next-generation sequencing panel was attempted in 24/28, with sufficient informative material in 15 (51.7%). Tumors comprised 4 distinct groups: driver mutations in H3F3A (brainstem=4; cerebellum=2), IDH1 (brainstem=4; cerebellum=4), TERT promotor mutation (brainstem=0; cerebellum=3), and none of these (n=5), with the latter harboring mutations of TP53, PDGFRA, ATRX, NF1, and RB1. All TERT promoter-mutant cases were IDH-wild-type and arose within the cerebellum. To date, 20 patients have died of disease, with a median survival of 16.3 months, 1-year survival of 67.5%. Median survival within the subgroups included: H3F3A=16.4 months, IDH mutant=113.4 months, and TERT promoter mutant=12.9 months. These findings suggest that PF diffuse gliomas affecting adults show molecular heterogeneity, which may be associated with patient outcomes and possible response to therapy, and supports the utility of molecular testing in these tumors.

Cerebellar high-grade glioma with H3 K27M mutation: illustrative case

BACKGROUND

Diffuse midline glioma H3 K27M-mutant is a distinct subtype of glial tumors newly introduced in the revised fourth edition of the World Health Organization Classification of Tumours of the Central Nervous System. They are aggressive pediatric tumors with a poor prognosis but have also been reported in adults.

OBSERVATIONS

The authors present the case of a man in his 60s who presented with rotatory vertigo, taste disorder, and right facial paralysis. Magnetic resonance imaging showed a tumor expanding from the cerebellum to the pons, which was histologically identified as glioblastoma, grade IV, IDH wild type. After tumor resection, the patient received chemoradiotherapy but showed only a partial response. His condition gradually worsened, and he died of progressive disease 12 months postoperation, after which an autopsy was performed. Tumor cells with a high nuclear-to-cytoplasm ratio were immunohistochemically analyzed and found to test positive for H3 K27M and negative for H3 K27me3. Furthermore, mutational analysis revealed HIST1H3B K27M mutation, and the tumor was finally identified as a high-grade glioma H3 K27M-mutant. The tumor invaded widely along the cerebral ventricle and disseminated to the spinal cord.

LESSONS

When a glioblastoma shows localization or dissemination patterns different from those of typical glioblastoma, an H3 K27M-mutant glioma should be suspected.

Primary cerebellar glioblastomas in children: clinical presentation and management

Pediatric cerebellar glioblastomas (pcGBMs) are rare and their characteristics remain ill-defined. We conducted a retrospective analysis of pediatric cerebellar glioblastomas who underwent surgery from 2008 to 2019 in our department. Besides, we performed a literature review of the literature data on pcGBMs. Ten children with mean age of 9.4 years were included. During the follow-up, six patients died with mean survival time of 11.7 months, four patients survived with mean follow-up of 28 months. Seven patients underwent molecular analysis, no patients detected IDH1 mutations, four patients (57.1%) had H3K27M mutations, and two patients (28.6%) had MGMT promoter methylation. The literature review identified 38 pcGBMs cases (including ours), with mean age of 8.84 ± 4.20 years (range, 1-16 years). Increased ICP was the commonest sign. Eighteen (47.4%) patients underwent GTR and fifteen (45.5%) patients received STR. Postoperative radiation (RT) was conducted in 28 patients (75.7%) and 23 patients (65.7%) received chemotherapy. During the follow-up, 25 patients died with mean survival time of 12.21 months and 11 patients survived with average follow-up of 29.3 months. Kaplan-Meier survival depicted chemotherapy (P < 0.001) or radiation (P < 0.001) had positive impact on overall survival. Multivariate analysis revealed chemotherapy was a significant predictor of survival with a hazard ratio of 3.264 (P = 0.038). Our study found mean overall survival time for pcGBMs patients was 12.21 months. PcGBMs may have distinct molecular features, with higher incidence of H3K27M mutation and were always IDH1 wild-type. We recommend the routine postoperative radiotherapy and chemotherapy in pcGBMs.