The evolving role for re-irradiation in the management of recurrent grade 4 glioma.

Although significant gains have been realized in the management of grade 4 glioma, the majority of these patients will ultimately suffer local recurrence within the prior field of treatment. Clearly, novel local treatment strategies are required to improve patient outcomes. Concerns of toxicity have limited enthusiasm for the utilization of re-irradiation as a treatment option. However, using modern imaging technology and precision radiotherapy delivery techniques re-irradiation has proven a feasible option achieving both a palliative benefit and prolongation of survival with low toxicity rates. The evolution of re-irradiation as a treatment modality for recurrent grade 4 glioma is reviewed. In addition, potential targeted radiosensitizers to be used in conjunction with re-irradiation are also discussed.

Dissection of transcriptomic and epigenetic heterogeneity of grade 4 gliomas: implications for prognosis.

BACKGROUND: Grade 4 glioma is the most aggressive and currently incurable brain tumor with a median survival of one year in adult patients. Elucidating novel transcriptomic and epigenetic contributors to the molecular heterogeneity underlying its aggressiveness may lead to improved clinical outcomes. METHODS: To identify grade 4 glioma -associated 5-hydroxymethylcytosine (5hmC) and transcriptomic features as well as their cross-talks, genome-wide 5hmC and transcriptomic profiles of tissue samples from 61 patients with grade 4 gliomas and 9 normal controls were obtained for differential and co-regulation/co-modification analyses. Prognostic models on overall survival based on transcriptomic features and the 5hmC modifications summarized over genic regions (promoters, gene bodies) and brain-derived histone marks were developed using machine learning algorithms. RESULTS: Despite global reduction, the majority of differential 5hmC features showed higher modification levels in grade 4 gliomas as compared to normal controls. In addition, the bi-directional correlations between 5hmC modifications over promoter regions or gene bodies and gene expression were greatly disturbed in grade 4 gliomas regardless of IDH1 mutation status. Phenotype-associated co-regulated 5hmC-5hmC modules and 5hmC-mRNA modules not only are enriched with different molecular pathways that are indicative of the pathogenesis of grade 4 gliomas, but also are of prognostic significance comparable to IDH1 mutation status. Lastly, the best-performing 5hmC model can predict patient survival at a much higher accuracy (c-index = 74%) when compared to conventional prognostic factor IDH1 (c-index = 57%), capturing the molecular characteristics of tumors that are independent of IDH1 mutation status and gene expression-based molecular subtypes. CONCLUSIONS: The 5hmC-based prognostic model could offer a robust tool to predict survival in patients with grade 4 gliomas, potentially outperforming existing prognostic factors such as IDH1 mutations. The crosstalk between 5hmC and gene expression revealed another layer of complexity underlying the molecular heterogeneity in grade 4 gliomas, offering opportunities for identifying novel therapeutic targets.

Treatment Patterns and Outcomes of Patients with Grade 4 Glioma Treated with Radiation during the COVID-19 Pandemic.

During the first year of the COVID-19 pandemic there was a global disruption in the provision of healthcare. Grade 4 gliomas are rapidly progressive tumors, and these patients are at risk of poorer outcomes due to delays in diagnosis or treatment. We retrospectively evaluated the impact of the pandemic on treatment patterns and outcomes of patients with grade 4 gliomas in British Columbia. We identified a cohort of 85 patients treated with radiotherapy between March 2020-2021 (COVID era) and compared baseline characteristics, treatments, and outcomes with a control cohort of 79 patients treated between March 2018-2019 (pre-COVID era). There were fewer patients treated with radiotherapy over age 65 in the COVID era compared to the pre-COVID era (p = 0.037). Significantly more patients were managed with biopsy relative to partial or gross total resection during the COVID era compared to the pre-COVID era (p = 0.04), but there were no other significant differences in time to assessment, time to treatment, or administration of adjuvant therapy. There was no difference in overall survival between eras (p = 0.189). In this assessment of outcomes of grade 4 gliomas during the pandemic, we found that despite less aggressive surgical intervention during the COVID era, outcomes were similar between eras.

Translational significance of CDKN2A/B homozygous deletion in isocitrate dehydrogenase-mutant astrocytoma.

Isocitrate dehydrogenase (IDH) 1 or 2 mutations confer a favorable prognosis compared to IDH-wildtype in astrocytoma, frequently denoting a lower grade malignancy. However, recent molecular profiling has identified specific aggressive tumor subgroups with clear clinical prognostic implications that are independent of histologic grading. The homozygous deletion of CDKN2A/B is the strongest implicated independent indicator of the poor prognosis within IDH-mutant astrocytoma, and the identification of this alteration in these lower histologic grade tumors transforms their biology toward an aggressive grade 4 phenotype clinically. CDKN2A/B homozygous deletion is now sufficient to define a grade 4 tumor in IDH-mutant astrocytomas regardless of histologic appearance, yet there are currently no effective molecularly informed targeted therapies for these tumors. The biological impact of CDKN2A/B homozygous deletion in IDH-mutant tumors and the optimal treatment strategy for this molecular subgroup remains insufficiently explored. Here we review the current understanding of the translational significance of homozygous deletion of CDKN2A/B gene expression in IDH-mutant astrocytoma and associated diagnostic and therapeutic implications.

Contribution of Oxidative Stress Induced by Sonodynamic Therapy to the Calcium Homeostasis Imbalance Enhances Macrophage Infiltration in Glioma Cells.

BACKGROUND: To better understand the Ca2+ overload mechanism of SDT killing gliomas, we examined the hypothesis that the early application of the mechanosensitive Ca2+ channel Piezo1 antagonist (GsMTx4) could have a better anti-tumor effect. METHODS: The in vitro effect of low-energy SDT combined with GsMTx4 or agonist Yoda 1 on both the ROS-induced distribution of Ca2+ as well as on the opening of Piezo1 and the dissociation and polymerization of the Ca2+ lipid complex were assessed. The same groups were also studied to determine their effects on both tumor-bearing BALB/c-nude and C57BL/6 intracranial tumors, and their effects on the tumor-infiltrating macrophages were studied as well. RESULTS: It was determined that ultrasound-activated Piezo1 contributes to the course of intracellular Ca2+ overload, which mediates macrophages (M1 and M2) infiltrating under the oxidative stress caused by SDT. Moreover, we explored the effects of SDT based on the dissociation of the Ca2+ lipid complex by inhibiting the expression of fatty acid binding protein 4 (FABP4). The Piezo1 channel was blocked early and combined with SDT treatment, recruited macrophages in the orthotopic transplantation glioma model. CONCLUSIONS: SDT regulates intracellular Ca2+ signals by upregulating Piezo1 leading to the inhibition of the energy supply from lipid and recruitment of macrophages. Therefore, intervening with the function of the Ca2+ channel on the glioma cell membrane in advance is likely to be the key factor to obtain a better effect combined with SDT treatment.