Increased subventricular zone radiation dose correlates with survival in glioblastoma patients after gross total resection

IGFBP-2 and IGF-II: Key Components of the Neural Stem Cell Niche? Implications for Glioblastoma Pathogenesis

Glioblastoma is a fatal and aggressive cancer with no cure. It is becoming increasingly clear that glioblastoma initiation is a result of adult neural stem cell (NSC) transformation-most likely those within the subventricular zone (SVZ). Indeed, transcriptomic analysis indicates that glioblastomas are reminiscent of a neurodevelopmental hierarchy, in which neural stem and progenitor markers are widely expressed by tumour stem-like cells. However, NSC fates and the cues that drive them are poorly understood. Studying the crosstalk within NSC niches may better inform our understanding of glioblastoma initiation and development. Insulin-like growth factor binding protein 2 (IGFBP-2) has a well-established prognostic role in glioblastoma, and cell-based mechanistic studies show the independent activation of downstream oncogenic pathways. However, IGFBP-2 is more commonly recognised as a modulator of insulin-like growth factors (IGFs) for receptor tyrosine kinase signal propagation or attenuation. In the adult human brain, both IGFBP-2 and IGF-II expression are retained in the choroid plexus (ChP) and secreted into the cerebral spinal fluid (CSF). Moreover, secretion by closely associated cells and NSCs themselves position IGFBP-2 and IGF-II as interesting factors within the NSC niche. In this review, we will highlight the experimental findings that show IGFBP-2 and IGF-II influence NSC behaviour. Moreover, we will link this to glioblastoma biology and demonstrate the requirement for further analysis of these factors in glioma stem cells (GSCs).

Specific radiosensitivity of brain structures (areas or regions) and cognitive impairment after focal or whole brain radiotherapy: A review

Delayed neurocognitive impairment is observed following encephalic radiotherapy, including brain parts (areas), leading to a substantial deterioration of the quality of life. These delayed radiotherapy side effects are variable in terms of intensity of symptoms and time of occurrence, characterized by minor-to-severe cognitive deficits, such as attention or memory disorders and/or dysexecutive syndrome. However, the precise mechanisms leading to these cognitive disorders remain mostly unknown. Various tissue alterations have been reported after brain radiotherapy, in specific brain structures as the hippocampus, the cerebral white matter or the cerebral cortex. Sparing these structures during brain radiotherapy may be a potential approach to limit the development of late cognitive impairment; however, few dose constraints have been published regarding brain areas (regions) involved in cognitive functions. The main purposes of this literature review are to report the pathophysiological process leading to the radiation-induced cognitive impairment, to describe the tolerance and radiological modifications induced by radiation of specific healthy cerebral tissues, to better understand their radiosensitivity and to describe potential improvements.

Ependymal invasion in High-Grade Glioma. Impact on surgical, functional outcomes, and survival rates. Experience in a Latin-American center

OBJECTIVE

Analyze the impact of ependymal invasion in high-grade gliomas (HGG) on surgical, functional outcomes, and survival rates.

MATERIALS AND METHODS

Retrospective, single-center, analytical study of a cohort of adult patients who underwent surgery for HGG at an Argentine center between 2013 and 2023. Patients with Grade IV supratentorial gliomas, with at least 3 months of follow-up and pre-/postoperative volumetric MRI were evaluated for the presence of ependymal invasion and its impact on prognosis.

RESULTS

Out of 591 patients undergoing HGG surgery, 263 met the inclusion criteria, with a mean follow-up of 24.8 months (range 5-141). The mean age was 58.5 years with a predominance of male patients (63%). Glioblastomas accounted for 80% of cases, with frontal (28.5%) and temporal (21.6%) lobes as the most frequent tumor locations. Mean preoperative volume was 27.2 cm³, and the mean KPS at surgery was 82. Ependymal invasion was identified in 83 patients (31.5%) and was associated with significantly worse progression-free survival (PFS) and overall survival (OS). These patients had an increased risk of and earlier onset of multicentricity and leptomeningeal spread. Ependymal invasion also negatively impacted the extent of resection, increasing subtotal resections, and it was also associated with a higher risk of complications such as hydrocephalus and CSF leaks.

CONCLUSION

Ependymal invasion significantly and independently impacts prognosis of patients with HGG. These findings underscore the importance of recognizing ependymal invasion as a key prognostic factor to guide the management and treatment strategies for affected patients.

[Glioblastoma and its interaction with neurogenesis]

Glioblastoma (GBM) is the most frequent and aggressive malignant primary tumor of the central nervous system in adults, with an incidence of 3.23 per 100,000 people. Despite the existence of various therapeutic approaches, the absence of a cure and the unfavorable prognosis persist for this neoplasm, with a median survival of approximately 8-15 months and a 5-year survival rate of 6.9%. In this review, we address the epidemiology, histopathology, molecular characteristics, and treatment of GBM. We highlight the relationship of GBM with the microenvironment in the lateral ventricle wall and the cerebrospinal fluid. The location of GBM in this region results in more aggressive tumors and shorter life expectancy for patients. Understanding the malignancy mechanisms that hinder remission, treatment, and positive prognosis opens the possibility of improving diagnostic and therapeutic interventions against GBM.

Cell-specific cross-talk proteomics reveals cathepsin B signaling as a driver of glioblastoma malignancy near the subventricular zone

Glioblastoma (GBM) is the most prevalent and aggressive malignant primary brain tumor. GBM proximal to the lateral ventricles (LVs) is more aggressive, potentially because of subventricular zone contact. Despite this, cross-talk between GBM and neural stem/progenitor cells (NSC/NPCs) is not well understood. Using cell-specific proteomics, we show that LV-proximal GBM prevents neuronal maturation of NSCs through induction of senescence. In addition, GBM brain tumor-initiating cells (BTICs) increase expression of cathepsin B (CTSB) upon interaction with NPCs. Lentiviral knockdown and recombinant protein experiments reveal that both cell-intrinsic and soluble CTSB promote malignancy-associated phenotypes in BTICs. Soluble CTSB stalls neuronal maturation in NPCs while promoting senescence, providing a link between LV-tumor proximity and neurogenesis disruption. Last, we show LV-proximal CTSB up-regulation in patients, showing the relevance of this cross-talk in human GBM biology. These results demonstrate the value of proteomic analysis in tumor microenvironment research and provide direction for new therapeutic strategies in GBM.

Clinicogenetic characteristics and the effect of radiation on the neural stem cell niche in subventricular zone-contacting glioblastoma

BACKGROUND AND PURPOSE

Neural stem cells (NSCs) in the subventricular zone (SVZ) are recognized as the cellular origin of glioblastoma (GBM) and a potential therapeutic target. However, the characteristics of SVZ contacting GBM (SVZ + GBM) and radiotherapeutic strategies for NSCs are still controversial. Here, we investigated the clinicogenetic features of SVZ + GBM and evaluated the dose effect of NSC irradiation depending on SVZ involvement.

MATERIALS AND METHODS

We identified 125 patients with GBM treated with surgery followed by chemoradiotherapy. The genomic profiles were obtained by next-generation sequencing targeting 82 genes. NSCs in the SVZ and hippocampus were contoured using standardized methods, and dosimetric factors were analyzed. SVZ + GBM was defined as GBM with SVZ involvement in a T1 contrast-enhanced image. Progression-free survival (PFS) and overall survival (OS) were used as endpoints.

RESULTS

The number of patients with SVZ + GBM was 95 (76%). SVZ + GBM showed lower PFS than GBM without SVZ involvement (SVZ-GBM) (median 8.6 vs. 11.5 months, p = 0.034). SVZ contact was not associated with any specific genetic profile but was an independent prognostic factor in multivariate analysis. In SVZ + GBM, patients receiving high doses to the ipsilateral NSC region showed significantly better OS (HR = 1.89, p = 0.011) and PFS (HR = 1.77, p = 0.013). However, in SVZ-GBM, high doses to the ipsilateral NSC region were associated with worse OS (HR = 0.27, p = 0.013) and PFS (HR = 0.37, p = 0.035) in both univariate and multivariate analyses.

CONCLUSION

SVZ involvement in GBM was not associated with distinct genetic features. However, irradiation of NSCs was associated with better prognosis in patients with tumors contacting the SVZ.

Management and Molecular Characterization of Intraventricular Glioblastoma: A Single-Institution Case Series

While the central nervous system (CNS) tumor classification has increasingly incorporated molecular parameters, there is a paucity of literature reporting molecular alterations found in intraventricular glioblastoma (IVGBM), which are rare. We present a case series of nine IVGBMs, including molecular alterations found in standardized next-generation sequencing (NGS). We queried the clinical charts, operative notes, pathology reports, and radiographic images of nine patients with histologically confirmed IVGBM treated at our institution (1995-2021). Routine NGS was performed on resected tumor tissue of two patients. In this retrospective case series of nine patients (22% female, median (range) age: 64.3 (36-85) years), the most common tumor locations were the atrium of the right lateral ventricle (33%) and the septum pellucidum (33%). Five patients had preoperative hydrocephalus, which was managed with intraoperative external ventricular drains in three patients and ventriculoperitoneal shunts in one patient. Hydrocephalus was managed with subtotal resection of a fourth ventricular IVGBM in one patient. The most common surgical approach was transcortical intraventricular (56%). Gross total resection was achieved in two patients, subtotal resection was achieved in six patients, and one patient received a biopsy only. Immunohistochemistry for IDH1 R132H mutant protein was performed in four cases and was negative in all four. Genetic alterations common in glioblastoma, IDH-wildtype, were seen in two cases with available NGS data, including EGFR gene amplification, TERT promoter mutation, PTEN mutation, trisomy of chromosome 7, and monosomy of chromosome 10. Following surgical resection, four patients received adjuvant chemoradiation. Median survival among our cohort was 4.7 months (IQR: 0.9-5.8 months). Management of IVGBM is particularly challenging due to their anatomical location, presentation with obstructive hydrocephalus, and fast growth, necessitating prompt intervention. Additional studies are needed to better understand the genetic landscape of IVGBM compared to parenchymal glioblastoma and may further elucidate the unique pathophysiology of these rare tumors.

Cell-specific crosstalk proteomics reveals cathepsin B signaling as a driver of glioblastoma malignancy near the subventricular zone

Glioblastoma (GBM) is the most prevalent and aggressive malignant primary brain tumor. GBM proximal to the lateral ventricles (LVs) is more aggressive, potentially due to subventricular zone (SVZ) contact. Despite this, crosstalk between GBM and neural stem/progenitor cells (NSC/NPCs) is not well understood. Using cell-specific proteomics, we show that LV-proximal GBM prevents neuronal maturation of NSCs through induction of senescence. Additionally, GBM brain tumor initiating cells (BTICs) increase expression of CTSB upon interaction with NPCs. Lentiviral knockdown and recombinant protein experiments reveal both cell-intrinsic and soluble CTSB promote malignancy-associated phenotypes in BTICs. Soluble CTSB stalls neuronal maturation in NPCs while promoting senescence, providing a link between LV-tumor proximity and neurogenesis disruption. Finally, we show LV-proximal CTSB upregulation in patients, showing the relevance of this crosstalk in human GBM biology. These results demonstrate the value of proteomic analysis in tumor microenvironment research and provide direction for new therapeutic strategies in GBM.

Highlights

Periventricular GBM is more malignant and disrupts neurogenesis in a rodent model.Cell-specific proteomics elucidates tumor-promoting crosstalk between GBM and NPCs.NPCs induce upregulated CTSB expression in GBM, promoting tumor progression.GBM stalls neurogenesis and promotes NPC senescence via CTSB.

Supramaximal Resection Can Prolong the Survival of Patients with Cortical Glioblastoma: A Volumetric Study

We aimed to retrospectively determine the resection rate of fluid-attenuated inversion recovery (FLAIR) lesions to evaluate the clinical effects of supramaximal resection (SMR) on the survival of patients with glioblastoma (GBM). Thirty-three adults with newly diagnosed GBM who underwent gross total tumor resection were enrolled. The tumors were classified into cortical and deep-seated groups according to their contact with the cortical gray matter. Pre- and postoperative FLAIR and gadolinium-enhanced T1-weighted imaging tumor volumes were measured using a three-dimensional imaging volume analyzer, and the resection rate was calculated. To evaluate the association between SMR rate and outcome, we subdivided patients whose tumors were totally resected into the SMR and non-SMR groups by moving the threshold value of SMR in 10% increments from 0% and compared their overall survival (OS) change. An improvement in OS was observed when the threshold value of SMR was 30% or more. In the cortical group (n = 23), SMR (n = 8) tended to prolong OS compared with gross total resection (GTR) (n = 15), with the median OS of 69.6 and 22.1 months, respectively (p = 0.0945). Contrastingly, in the deep-seated group (n = 10), SMR (n = 4) significantly shortened OS compared with GTR (n = 6), with median OS of 10.2 and 27.9 months, respectively (p = 0.0221). SMR could help prolong OS in patients with cortical GBM when 30% or more volume reduction is achieved in FLAIR lesions, although the impact of SMR for deep-seated GBM must be validated in larger cohorts.

Prognostic analysis and nomogram construction for older patients with IDH-wild-type glioblastoma

As many countries face an ageing population, the number of older patients with glioblastoma (GB) is increasing. Thus, there is an urgent need for prognostic models to aid in treatment decision-making and life planning. A total of 98 patients with isocitrate dehydrogenase (IDH)-wild-type GB aged ≥65 years were analysed from January 2012 to January 2020. Independent prognostic factors were identified by prognostic analysis. Using the independent prognostic factors for overall survival (OS), a nomogram was constructed by R software to predict the prognosis of older patients with IDH-wild-type GB. The concordance index (C-index) and receiver operating characteristic (ROC) curve were used to assess model discrimination, and the calibration curve was used to assess model calibration. Prognostic analysis showed that the extent of resection (EOR), adjusted Charlson comorbidity index (ACCI), O6-methylguanine-DNA methyltransferase (MGMT) methylation status, postoperative radiotherapy, and postoperative temozolomide (TMZ) chemotherapy were independent prognostic factors for OS. MGMT methylation status and subventricular zone (SVZ) involvement were independent prognostic factors for progression-free survival (PFS). A nomogram was constructed based on EOR, ACCI, MGMT methylation status, postoperative radiotherapy and postoperative TMZ chemotherapy to predict the 6-month, 12-month and 18-month OS of older patients with IDH-wild-type GB. The C-index of the nomogram was 0.72, and the ROC curves showed that the areas under the curve (AUCs) at 6, 12 and 18 months were 0.874, 0.739 and 0.779, respectively. The calibration plots showed that the nomogram was in good agreement with the actual observations in predicting the OS of older patients with IDH-wild-type GB. Older patients with IDH-wild-type GB can benefit from gross total resection (GTR), postoperative radiotherapy and postoperative TMZ chemotherapy. A high ACCI score and MGMT nonmethylation are poor prognostic factors. We constructed a nomogram including the ACCI to facilitate clinical decision-making and follow-up interval selection.

The anatomy of neuroepithelial tumours

Many neurological conditions conceal specific anatomical patterns. Their study contributes to the understanding of disease biology and to tailored diagnostics and therapy. Neuroepithelial tumours exhibit distinct anatomical phenotypes and spatiotemporal dynamics that differ from those of other brain tumours. Brain metastases display a preference for the cortico-subcortical boundaries of watershed areas and have a predominantly spherical growth. Primary CNS lymphomas localize to the white matter and generally invade along fibre tracts. In neuroepithelial tumours, topographic probability mapping and unsupervised topological clustering have identified an inherent radial anatomy and adherence to ventriculopial configurations of specific hierarchical orders. Spatiotemporal probability and multivariate survival analyses have identified a temporal and prognostic sequence underlying the anatomical phenotypes of neuroepithelial tumours. Gradual neuroepithelial de-differentiation and declining prognosis follow (i) an expansion into higher order radial units; (ii) a subventricular spread; and (iii) the presence of mesenchymal patterns (expansion along white matter tracts, leptomeningeal or perivascular invasion, CSF spread). While different pathophysiological hypotheses have been proposed, the cellular and molecular mechanisms dictating this anatomical behaviour remain largely unknown. Here we adopt an ontogenetic approach towards the understanding of neuroepithelial tumour anatomy. Contemporary perception of histo- and morphogenetic processes during neurodevelopment permit us to conceptualize the architecture of the brain into hierarchically organized radial units. The anatomical phenotypes in neuroepithelial tumours and their temporal and prognostic sequences share remarkable similarities with the ontogenetic organization of the brain and the anatomical specifications that occur during neurodevelopment. This macroscopic coherence is reinforced by cellular and molecular observations that the initiation of various neuroepithelial tumours, their intratumoural hierarchy and tumour progression are associated with the aberrant reactivation of surprisingly normal ontogenetic programs. Generalizable topological phenotypes could provide the basis for an anatomical refinement of the current classification of neuroepithelial tumours. In addition, we have proposed a staging system for adult-type diffuse gliomas that is based on the prognostically critical steps along the sequence of anatomical tumour progression. Considering the parallels in anatomical behaviour between different neuroepithelial tumours, analogous staging systems may be implemented for other neuroepithelial tumour types and subtypes. Both the anatomical stage of a neuroepithelial tumour and the spatial configuration of its hosting radial unit harbour the potential to stratify treatment decisions at diagnosis and during follow-up. More data on specific neuroepithelial tumour types and subtypes are needed to increase the anatomical granularity in their classification and to determine the clinical impact of stage-adapted and anatomically tailored therapy and surveillance.

Targeting the neural stem cells in subventricular zone for the treatment of glioblastoma: an update from preclinical evidence to clinical interventions

BACKGROUND

Glioblastoma is one of the most common and aggressive adult brain tumors. The conventional treatment strategy, surgery combined with chemoradiotherapy, did not change the fact that the recurrence rate was high and the survival rate was low. Over the years, accumulating evidence has shown that the subventricular zone has an important role in the recurrence and treatment resistance of glioblastoma. The human adult subventricular zone contains neural stem cells and glioma stem cells that are probably a part of reason for therapy resistance and recurrence of glioblastoma.

MAIN BODY

Over the years, both bench and bedside evidences strongly support the view that the presence of neural stem cells and glioma stem cells in the subventricular zone may be the crucial factor of recurrence of glioblastoma after conventional therapy. It emphasizes the necessity to explore new therapy strategies with the aim to target subventricular zone to eradicate neural stem cells or glioma stem cells. In this review, we summarize the recent preclinical and clinical advances in targeting neural stem cells in the subventricular zone for glioblastoma treatment, and clarify the prospects and challenges in clinical application.

CONCLUSIONS

Although there remain unresolved issues, current advances provide us with a lot of evidence that targeting the neural stem cells and glioma stem cells in subventricular zone may have the potential to solve the dilemma of glioblastoma recurrence and treatment resistance.

Therapy Resistance of Glioblastoma in Relation to the Subventricular Zone: What Is the Role of Radiotherapy?

Glioblastoma is a highly heterogeneous primary malignant brain tumor with marked inter-/intratumoral diversity and a poor prognosis. It may contain a population of neural stem cells (NSC) and glioblastoma stem cells that have the capacity for migration, self-renewal and differentiation. While both may contribute to resistance to therapy, NSCs may also play a role in brain tissue repair. The subventricular zone (SVZ) is the main reservoir of NSCs. This study investigated the impact of bilateral SVZ radiation doses on patient outcomes. We included 147 patients. SVZs were delineated and the dose administered was extracted from dose–volume histograms. Tumors were classified based on their spatial relationship to the SVZ. The dose and outcome correlations were analyzed using the Kaplan–Meier and Cox proportional hazards regression methods. Median progression-free survival (PFS) was 7 months (range: 4–11 months) and median overall survival (OS) was 14 months (range: 9–23 months). Patients with an ipsilateral SVZ who received ≥50 Gy showed significantly better PFS (8 versus 6 months; p < 0.001) and OS (16 versus 11 months; p < 0.001). Furthermore, lower doses (<32 Gy) to the contralateral SVZ were associated with improved PFS (8 versus 6 months; p = 0.030) and OS (15 versus 11 months; p = 0.001). Targeting the potential tumorigenic cells in the ipsilateral SVZ while sparing contralateral NSCs correlated with an improved outcome. Further studies should address the optimization of dose distribution with modern radiotherapy techniques for the areas surrounding infiltrated and healthy SVZs.

Meningeosis Neoplastica in Patients with Glioblastoma: Analysis of 36 Cases

BACKGROUND

Meningeosis neoplastica is a rare manifestation of high-grade gliomas and is usually associated with a devastating outcome. The aim of this bicenter series was to investigate the clinical course and outcome of patients with meningiosis neoplastica.

METHODS

This case series included patients in whom surgery was performed for World Health Organization grade IV primary and secondary glioblastoma (GBM) at the University Medical Center Göttingen, Göttingen, Germany between 2009 and 2021 and Burdenko Institute of Neurosurgery, Moscow, Russia between 2012 and 2018. Inclusion criteria were manifestation of clinical and neuroradiologic signs of leptomeningeal, ependymal, or spinal dissemination of GBM at various time points during the course of the disease.

RESULTS

Meningeosis neoplastica was found in 36 patients. Nine patients developed spinal metastases and 12 ependymal dissemination and 15 patients had a leptomeningeal manifestation of high-grade glioma. The median age of patients at first diagnosis of primary tumor was 56 years. Typical symptoms were headache, nausea, vomiting, and acute paraplegia. The median overall survival was 11 months and progression-free survival was 8 months. Meningeosis neoplastica developed a median 2 months after the initial tumor diagnosis. Salvage therapies included ventriculoperitoneal shunting, decompression of spinal metastases, and spinal radiation therapy. The median time between meningeosis manifestation and death was 3 months.

CONCLUSIONS

Meningeosis neoplastica is a rare manifestation of GBM. It has a poor prognosis. The overall survival after the manifestation of meningeosis was barely longer than 3 months. Salvage therapies did not improve the outcome in our patient cohort.

Liquid biopsy with multiplex ligation-dependent probe amplification targeting cell-free tumor DNA in cerebrospinal fluid from patients with adult diffuse glioma

Background

Copy number alterations (CNAs) are common in diffuse gliomas and have been shown to have diagnostic significance. While liquid biopsy for diffuse glioma has been widely investigated, techniques for detecting CNAs are currently limited to methods such as next-generation sequencing. Multiplex ligation-dependent probe amplification (MLPA) is an established method for copy number analysis in pre-specified loci. In this study, we investigated whether CNAs could be detected by MLPA using patients' cerebrospinal fluid (CSF).

Methods

Twenty-five cases of adult diffuse glioma with CNAs were selected. Cell-free DNA (cfDNA) was extracted from the CSF, and DNA sizes and concentrations were recorded. Twelve samples, which had appropriate DNA sizes and concentrations, were subsequently used for analysis.

Results

MLPA could be successfully performed in all 12 cases, and the detected CNAs were concordant with those detected using tumor tissues. Cases with epidermal growth factor receptor (EGFR) amplification, combination of gain of chromosome 7 and loss of chromosome 10, platelet-derived growth factor receptor alpha amplification, cyclin-dependent kinase 4 amplification, and cyclin-dependent kinase inhibitor 2A (CDKN2A) homozygous deletion were clearly distinguished from those with normal copy numbers. Moreover, EGFR variant III was accurately detected based on CNA.

Conclusions

Thus, our results demonstrate that copy number analysis can be successfully performed by MLPA of cfDNA extracted from the CSF of patients with diffuse glioma.

Relapse patterns and radiation dose exposure in IDH wild-type glioblastoma at first radiographic recurrence following chemoradiation

PURPOSE

To quantify the radiation dose distribution and lesion morphometry (shape) at baseline, prior to chemoradiation, and at the time of radiographic recurrence in patients with glioblastoma (GBM).

METHODS

The IMRT dose distribution, location of the center of mass, sphericity, and solidity of the contrast enhancing tumor at baseline and the time of tumor recurrence was quantified in 48 IDH wild-type GBM who underwent postoperative IMRT (2 Gy daily for total of 60 Gy) with concomitant and adjuvant temozolomide.

RESULTS

Average radiation dose within enhancing tumor at baseline and recurrence was ≥ 60 Gy. Centroid location of the enhancing tumor shifted an average of 11.3 mm at the time of recurrence with respect to pre-IMRT location. A positive correlation was observed between change in centroid location and PFS in MGMT methylated patients (P = 0.0007) and Cox multivariate regression confirmed centroid distance from baseline was associated with PFS when accounting for clinical factors (P = 0.0189). Lesion solidity was higher at recurrence compared to baseline (P = 0.0118). Tumors that progressed > 12 weeks after IMRT were significantly more spherical (P = 0.0094).

CONCLUSION

Most GBMs recur local within therapeutic IMRT doses; however, tumors with longer PFS occurred further from the original tumor location and were more solid and/or nodular.

cGAS-STING pathway targeted therapies and their applications in the treatment of high-grade glioma

Median survival of patients with glioblastoma (GBM) treated with standard of care which consists of maximal safe resection of the contrast-enhancing portion of the tumor followed by radiation therapy with concomitant adjuvant temozolomide (TMZ) remains 15 months. The tumor microenvironment (TME) is known to contain immune suppressive myeloid cells with minimal effector T cell infiltration. Stimulator of interferon genes (STING) is an important activator of immune response and results in production of Type 1 interferon and antigen presentation by myeloid cells. This review will discuss important developments in STING agonists, potential biomarkers for STING response, and new combinatorial therapeutic approaches in gliomas.

Repeatability of radiotherapy dose-painting prescriptions derived from a multiparametric magnetic resonance imaging model of glioblastoma infiltration

•

Magnetic resonance imaging was used to derive dose-painting prescriptions in glioma.

•

Dose prescriptions derived from magnetic resonance imaging are highly repeatable.

•

Dose-painting plans are more repeatable than their dose prescriptions.

Background and purpose

Glioblastoma (GBM) patients have a dismal prognosis. Tumours typically recur within months of surgical resection and post-operative chemoradiation. Multiparametric magnetic resonance imaging (mpMRI) biomarkers promise to improve GBM outcomes by identifying likely regions of infiltrative tumour in tumour probability (TP) maps. These regions could be treated with escalated dose via dose-painting radiotherapy to achieve higher rates of tumour control. Crucial to the technical validation of dose-painting using imaging biomarkers is the repeatability of the derived dose prescriptions. Here, we quantify repeatability of dose-painting prescriptions derived from mpMRI.

Materials and methods

TP maps were calculated with a clinically validated model that linearly combined apparent diffusion coefficient (ADC) and relative cerebral blood volume (rBV) or ADC and relative cerebral blood flow (rBF) data. Maps were developed for 11 GBM patients who received two mpMRI scans separated by a short interval prior to chemoradiation treatment. A linear dose mapping function was applied to obtain dose-painting prescription (DP) maps for each session. Voxel-wise and group-wise repeatability metrics were calculated for parametric, TP and DP maps within radiotherapy margins.

Results

DP maps derived from mpMRI were repeatable between imaging sessions (ICC > 0.85). ADC maps showed higher repeatability than rBV and rBF maps (Wilcoxon test, p = 0.001). TP maps obtained from the combination of ADC and rBF were the most stable (median ICC: 0.89).

Conclusions

Dose-painting prescriptions derived from a mpMRI model of tumour infiltration have a good level of repeatability and can be used to generate reliable dose-painting plans for GBM patients.

The DNA Double-Strand Break Repair in Glioma: Molecular Players and Therapeutic Strategies

Gliomas are the most frequent type of tumor in the central nervous system, which exhibit properties that make their treatment difficult, such as cellular infiltration, heterogeneity, and the presence of stem-like cells responsible for tumor recurrence. The response of this type of tumor to chemoradiotherapy is poor, possibly due to a higher repair activity of the genetic material, among other causes. The DNA double-strand breaks are an important type of lesion to the genetic material, which have the potential to trigger processes of cell death or cause gene aberrations that could promote tumorigenesis. This review describes how the different cellular elements regulate the formation of DNA double-strand breaks and their repair in gliomas, discussing the therapeutic potential of the induction of this type of lesion and the suppression of its repair as a control mechanism of brain tumorigenesis.

IDH-wild-type glioblastoma cell density and infiltration distribution influence on supramarginal resection and its impact on overall survival: a mathematical model

OBJECTIVE

Recent studies have proposed resection of the T2 FLAIR hyperintensity beyond the T1 contrast enhancement (supramarginal resection [SMR]) for IDH-wild-type glioblastoma (GBM) to further improve patients' overall survival (OS). GBMs have significant variability in tumor cell density, distribution, and infiltration. Advanced mathematical models based on patient-specific radiographic features have provided new insights into GBM growth kinetics on two important parameters of tumor aggressiveness: proliferation rate (ρ) and diffusion rate (D). The aim of this study was to investigate OS of patients with IDH-wild-type GBM who underwent SMR based on a mathematical model of cell distribution and infiltration profile (tumor invasiveness profile).

METHODS

Volumetric measurements were obtained from the selected regions of interest from pre- and postoperative MRI studies of included patients. The tumor invasiveness profile (proliferation/diffusion [ρ/D] ratio) was calculated using the following formula: ρ/D ratio = (4π/3)2/3 × (6.106/[VT21/1 - VT11/1])2, where VT2 and VT1 are the preoperative FLAIR and contrast-enhancing volumes, respectively. Patients were split into subgroups based on their tumor invasiveness profiles. In this analysis, tumors were classified as nodular, moderately diffuse, or highly diffuse.

RESULTS

A total of 101 patients were included. Tumors were classified as nodular (n = 34), moderately diffuse (n = 34), and highly diffuse (n = 33). On multivariate analysis, increasing SMR had a significant positive correlation with OS for moderately and highly diffuse tumors (HR 0.99, 95% CI 0.98-0.99; p = 0.02; and HR 0.98, 95% CI 0.96-0.99; p = 0.04, respectively). On threshold analysis, OS benefit was seen with SMR from 10% to 29%, 10% to 59%, and 30% to 90%, for nodular, moderately diffuse, and highly diffuse, respectively.

CONCLUSIONS

The impact of SMR on OS for patients with IDH-wild-type GBM is influenced by the degree of tumor invasiveness. The authors' results show that increasing SMR is associated with increased OS in patients with moderate and highly diffuse IDH-wild-type GBMs. When grouping SMR into 10% intervals, this benefit was seen for all tumor subgroups, although for nodular tumors, the maximum beneficial SMR percentage was considerably lower than in moderate and highly diffuse tumors.

The Subventricular Zone in Glioblastoma: Genesis, Maintenance, and Modeling

Glioblastoma (GBM) is a malignant tumor with a median survival rate of 15-16 months with standard care; however, cases of successful treatment offer hope that an enhanced understanding of the pathology will improve the prognosis. The cell of origin in GBM remains controversial. Recent evidence has implicated stem cells as cells of origin in many cancers. Neural stem/precursor cells (NSCs) are being evaluated as potential initiators of GBM tumorigenesis. The NSCs in the subventricular zone (SVZ) have demonstrated similar molecular profiles and share several distinctive characteristics to proliferative glioblastoma stem cells (GSCs) in GBM. Genomic and proteomic studies comparing the SVZ and GBM support the hypothesis that the tumor cells and SVZ cells are related. Animal models corroborate this connection, demonstrating migratory patterns from the SVZ to the tumor. Along with laboratory and animal research, clinical studies have demonstrated improved progression-free survival in patients with GBM after radiation to the ipsilateral SVZ. Additionally, key genetic mutations in GBM for the most part carry regulatory roles in the SVZ as well. An exciting avenue towards SVZ modeling and determining its role in gliomagenesis in the human context is human brain organoids. Here we comprehensively discuss and review the role of the SVZ in GBM genesis, maintenance, and modeling.

The survival outcomes of molecular glioblastoma IDH-wildtype: a multicenter study

PURPOSE

Histological diagnosis of glioblastoma (GBM) was determined by the presence of necrosis or microvascular proliferation (histGBM). The 2021 WHO classification now considers IDH-wildtype diffuse astrocytic tumors without the histological features of glioblastoma (that would have otherwise been classified as grade 2 or 3) as molecular GBM (molGBM, WHO grade 4) if they harbor any of the following molecular abnormalities: TERT promoter mutation, EGFR amplification, or chromosomal + 7/- 10 copy changes. The objective of this study was to explore and compare the survival outcomes between histGBM and molGBM.

METHODS

Medical records for patients diagnosed with GBM at the three tertiary care academic centers of our institution from November 2017 to October 2021. Only patients who underwent adjuvant chemoradiation were included. Patients without molecular feature testing or with an IDH mutation were excluded. Univariable and multivariable analyses were performed to evaluate progression-free (PFS) and overall- survival (OS).

RESULTS

708 consecutive patients were included; 643 with histGBM and 65 with molGBM. Median PFS was 8 months (histGBM) and 13 months (molGBM) (p = 0.0237) and median OS was 21 months (histGBM) versus 26 months (molGBM) (p = 0.435). Multivariable analysis on the molGBM sub-group showed a worse PFS if there was contrast enhancement on MRI (HR 6.224 [CI 95% 2.187-17.714], p < 0.001) and a superior PFS on patients with MGMT methylation (HR 0.026 [CI 95% 0.065-0.655], p = 0.007).

CONCLUSIONS

molGBM has a similar OS but significantly longer PFS when compared to histGBM. The presence of contrast enhancement and MGMT methylation seem to affect the clinical behavior of this subset of tumors.

Irradiation of the subventricular zone and subgranular zone in high- and low-grade glioma patients: an atlas-based analysis on overall survival

BACKGROUND

Neural stem cells in the subventricular zone (SVZ) and subgranular zone (SGZ) are hypothesized to support growth of glioma. Therefore, irradiation of the SVZ and SGZ might reduce tumor growth and might improve overall survival (OS). However, it may also inhibit the repair capacity of brain tissue. The aim of this retrospective cohort study is to assess the impact of SVZ and SGZ radiotherapy doses on OS of patients with high-grade (HGG) or low-grade (LGG) glioma.

METHODS

We included 273 glioma patients who received radiotherapy. We created an SVZ atlas, shared openly with this work, while SGZ labels were taken from the CoBrA atlas. Next, SVZ and SGZ regions were automatically delineated on T1 MR images. Dose and OS correlations were investigated with Cox regression and Kaplan-Meier analysis.

RESULTS

Cox regression analyses showed significant hazard ratios for SVZ dose (univariate: 1.029/Gy, P < .001; multivariate: 1.103/Gy, P = .002) and SGZ dose (univariate: 1.023/Gy, P < .001; multivariate: 1.055/Gy, P < .001) in HGG patients. Kaplan-Meier analysis showed significant correlations between OS and high-/low-dose groups for HGG patients (SVZ: respectively 10.7 months (>30.33 Gy) vs 14.0 months (<30.33 Gy) median OS, P = .011; SGZ: respectively 10.7 months (>29.11 Gy) vs 15.5 months (<29.11 Gy) median OS, P < .001). No correlations between dose and OS were found for LGG patients.

CONCLUSION

Irradiation doses on neurogenic areas correlate negatively with OS in patients with HGG. Whether sparing of the SVZ and SGZ during radiotherapy improves OS, should be subject of prospective studies.

The effects of altered neurogenic microRNA levels and their involvement in the aggressiveness of periventricular glioblastoma

INTRODUCTION

Glioblastoma multiforme is the most common primary brain tumour, with the least favourable prognosis. Despite numerous studies and medical advances, it continues to be lethal, with an average life expectancy of 15 months after chemo-radiotherapy.

DEVELOPMENT

Recent research has addressed several factors associated with the diagnosis and prognosis of glioblastoma; one significant factor is tumour localisation, particularly the subventricular zone, which represents one of the most active neurogenic niches of the adult human brain. Glioblastomas in this area are generally more aggressive, resulting in unfavourable prognosis and a shorter life expectancy. Currently, the research into microRNAs (miRNA) has intensified, revealing different expression patterns under physiological and pathophysiological conditions. It has been reported that the expression levels of certain miRNAs, mainly those related to neurogenic processes, are dysregulated in oncogenic events, thus favouring gliomagenesis and greater tumour aggressiveness. This review discusses some of the most important miRNAs involved in subventricular neurogenic processes and their association with glioblastoma aggressiveness.

CONCLUSIONS

MiRNA regulation and function play an important role in the development and progression of glioblastoma; understanding the alterations of certain miRNAs involved in both differentiation and neural and glial maturation could help us to better understand the malignant characteristics of glioblastoma.

Efficacy of Whole-Ventricular Radiotherapy in Patients Undergoing Maximal Tumor Resection for Glioblastomas Involving the Ventricle

Background and Purpose

Patients with glioblastoma (GBM) involving the ventricles are at high risk of ventricle opening during surgery and potential ventricular tumor spread. We evaluated the effectiveness of whole-ventricular radiotherapy (WVRT) in reducing intraventricular seeding in patients with GBM and identified patients who could benefit from this approach.

Methods and Materials

We retrospectively reviewed the data of 382 patients with GBM who underwent surgical resection and temozolomide-based chemoradiotherapy. Propensity score matching was performed to compensate for imbalances in characteristics between patients who did [WVRT (+); n=59] and did not [WVRT (–); n=323] receive WVRT. Local, outfield, intraventricular, and leptomeningeal failure rates were compared.

Results

All patients in the WVRT (+) group had tumor ventricular involvement and ventricle opening during surgery. In the matched cohort, the WVRT (+) group exhibited a significantly lower 2-year intraventricular failure rate than the WVRT (–) group (2.1% vs. 11.8%; P=0.045), with no difference in other outcomes. Recursive partitioning analysis stratified the patients in the WVRT (–) group at higher intraventricular failure risk (2-year survival, 14.2%) due to tumor ventricular involvement, MGMT unmethylation, and ventricle opening. WVRT reduced the intraventricular failure rate only in high-risk patients (0% vs. 14.2%; P=0.054) or those with MGMT-unmethylated GBM in the matched cohort (0% vs. 17.3%; P=0.036).

Conclusions

WVRT reduced the intraventricular failure rate in patients with tumor ventricular involvement and ventricle opening during surgery. The MGMT-methylation status may further stratify patients who could benefit from WVRT. Further prospective evaluation of WVRT in GBM is warranted.

Anatomical phenotyping and staging of brain tumours

Unlike other tumors, the anatomical extent of brain tumors is not objectified and quantified through staging. Staging systems are based on understanding the anatomical sequence of tumor progression and its relationship to histopathological dedifferentiation and survival. The aim of this study was to describe the spatiotemporal phenotype of the most frequent brain tumor entities, to assess the association of anatomical tumor features with survival probability and to develop a staging system for WHO grade 2 and 3 gliomas and glioblastoma. Anatomical phenotyping was performed on a consecutive cohort of 1000 patients with first diagnosis of a primary or secondary brain tumor. Tumor probability in different topographic, phylogenetic and ontogenetic parcellation units was assessed on preoperative MRI through normalization of the relative tumor prevalence to the relative volume of the respective structure. We analyzed the spatiotemporal tumor dynamics by cross-referencing preoperative against preceding and subsequent MRIs of the respective patient. The association between anatomical phenotype and outcome defined prognostically critical anatomical tumor features at diagnosis. Based on a hypothesized sequence of anatomical tumor progression, we developed a three-level staging system for WHO grade 2 and 3 gliomas and glioblastoma. This staging system was validated internally in the original cohort and externally in an independent cohort of 300 consecutive patients. While primary central nervous system lymphoma showed highest probability along white matter tracts, metastases enriched along terminal arterial flow areas. Neuroepithelial tumors mapped along all sectors of the ventriculocortical axis, while adjacent units were spared, consistent with a transpallial behavior within phylo-ontogenetic radial units. Their topographic pattern correlated with morphogenetic processes of convergence and divergence of radial units during phylo- and ontogenesis. While a ventriculofugal growth dominated in neuroepithelial tumors, a gradual deviation from this neuroepithelial spatiotemporal behavior was found with progressive histopathological dedifferentiation. The proposed three-level staging system for WHO grade 2 and 3 gliomas and glioblastoma correlated with the degree of histological dedifferentiation and proved accurate in terms of survival upon both internal and external validation. In conclusion, this study identified specific spatiotemporal phenotypes in brain tumors through topographic probability and growth pattern assessment. The association of anatomical tumor features with survival defined critical steps in the anatomical sequence of neuroepithelial tumor progression, based on which a staging system for WHO grade 2 and 3 gliomas and glioblastoma was developed and validated.

Combination of the Distance From Tumor Edge to Subventricular Zone and IDH Mutation Predicts Prognosis of Patients With Glioma

Both subventricular zone (SVZ) contact and isocitrate dehydrogenase 1 (IDH1) mutation have been reported to be related to the outcome of glioma, respectively. However, far too little attention has been paid to the role of tumor edge-SVZ distance in the outcome of glioma. We aim to assess the value of tumor-SVZ distance, as well as combined tumor-SVZ distance and IDH status, in predicting the outcome of gliomas (WHO grade II-IV). Here, the MR images and clinical data from 146 patients were included in the current study. The relationship between survival and the tumor-SVZ distance as well as survival and combination of tumor-SVZ distance and IDH status were determined via univariate and multivariate analyses. In univariate analysis of tumor-SVZ distance, the patients were divided into three types (SVZ involvement, tumor-SVZ distance from 0 to 10 mm, and tumor-SVZ distance >10 mm). The results showed that the OS (p = 0.02) and PFS (p = 0.002) for the patients had a positive correlation with the tumor-SVZ distance. In addition, simple linear correlation found a significant relationship between the two parameters (OS and PFS) and tumor-SVZ distance in patients with non-SVZ-contacting glioma. Combination analysis of the tumor-SVZ distance and IDH status showed that IDH1 mutation and SVZ non-involvement enable favorable outcomes, whereas IDH1 wild type with SVZ involvement indicates a significantly worse prognosis in all patients. Moreover, in patients with non-SVZ-contacting glioma, IDH1 mutation concurrent with tumor-SVZ distance >10 mm has better OS and PFS. IDH1 wild type and tumor-SVZ distance from 0 to 10 mm suggest poorer OS and PFS. Multivariate analysis showed WHO grade IV, SVZ involvement, tumor-SVZ distance from 0 to 10 mm, IDH1 mutation, gross total resection, and chemotherapy serve as independent predictors of OS. WHO grade IV, SVZ involvement, tumor-SVZ distance from 0 to 10 mm, IDH1 mutation, and chemotherapy serve as independent predictors of PFS of patients with glioma. In conclusion, tumor-SVZ distance and IDH1 mutation status are the determinants affecting patient outcome.

Role and mechanism of neural stem cells of the subventricular zone in glioblastoma

Glioblastoma multiforme (GBM), the most frequently occurring malignant brain tumor in adults, remains mostly untreatable. Because of the heterogeneity of invasive gliomas and drug resistance associated with the tumor microenvironment, the prognosis is poor, and the survival rate of patients is low. Communication between GBMs and non-glioma cells in the tumor microenvironment plays a vital role in tumor growth and recurrence. Emerging data have suggested that neural stem cells (NSCs) in the subventricular zone (SVZ) are the cells-of-origin of gliomas, and SVZ NSC involvement is associated with the progression and recurrence of GBM. This review highlights the interaction between SVZ NSCs and gliomas, summarizes current findings on the crosstalk between gliomas and other non-glioma cells, and describes the links between SVZ NSCs and gliomas. We also discuss the role and mechanism of SVZ NSCs in glioblastoma, as well as the interventions targeting the SVZ and their therapeutic implications in glioblastoma. Taken together, understanding the biological mechanism of glioma-NSC interactions can lead to new therapeutic strategies for GBM.

Glioblastoma Proximity to the Lateral Ventricle Alters Neurogenic Cell Populations of the Subventricular Zone

Despite current strategies combining surgery, radiation, and chemotherapy, glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor in adults. Tumor location plays a key role in the prognosis of patients, with GBM tumors located in close proximity to the lateral ventricles (LVs) resulting in worse survival expectancy and higher incidence of distal recurrence. Though the reason for worse prognosis in these patients remains unknown, it may be due to proximity to the subventricular zone (SVZ) neurogenic niche contained within the lateral wall of the LVs. We present a novel rodent model to analyze the bidirectional signaling between GBM tumors and cells contained within the SVZ. Patient-derived GBM cells expressing GFP and luciferase were engrafted at locations proximal, intermediate, and distal to the LVs in immunosuppressed mice. Mice were either sacrificed after 4 weeks for immunohistochemical analysis of the tumor and SVZ or maintained for survival analysis. Analysis of the GFP+ tumor bulk revealed that GBM tumors proximal to the LV show increased levels of proliferation and tumor growth than LV-distal counterparts and is accompanied by decreased median survival. Conversely, numbers of innate proliferative cells, neural stem cells (NSCs), migratory cells and progenitors contained within the SVZ are decreased as a result of GBM proximity to the LV. These results indicate that our rodent model is able to accurately recapitulate several of the clinical aspects of LV-associated GBM, including increased tumor growth and decreased median survival. Additionally, we have found the neurogenic and cell division process of the SVZ in these adult mice is negatively influenced according to the presence and proximity of the tumor mass. This model will be invaluable for further investigation into the bidirectional signaling between GBM and the neurogenic cell populations of the SVZ.

Influence of supramarginal resection on survival outcomes after gross-total resection of IDH-wild-type glioblastoma

OBJECTIVE

The authors' goal was to use a multicenter, observational cohort study to determine whether supramarginal resection (SMR) of FLAIR-hyperintense tumor beyond the contrast-enhanced (CE) area influences the overall survival (OS) of patients with isocitrate dehydrogenase-wild-type (IDH-wt) glioblastoma after gross-total resection (GTR).

METHODS

The medical records of 888 patients aged ≥ 18 years who underwent resection of GBM between January 2011 and December 2017 were reviewed. Volumetric measurements of the CE tumor and surrounding FLAIR-hyperintense tumor were performed, clinical variables were obtained, and associations with OS were analyzed.

RESULTS

In total, 101 patients with newly diagnosed IDH-wt GBM who underwent GTR of the CE tumor met the inclusion criteria. In multivariate analysis, age ≥ 65 years (HR 1.97; 95% CI 1.01-2.56; p < 0.001) and contact with the lateral ventricles (HR 1.59; 95% CI 1.13-1.78; p = 0.025) were associated with shorter OS, but preoperative Karnofsky Performance Status ≥ 70 (HR 0.47; 95% CI 0.27-0.89; p = 0.006), MGMT promotor methylation (HR 0.63; 95% CI 0.52-0.99; p = 0.044), and increased percentage of SMR (HR 0.99; 95% CI 0.98-0.99; p = 0.02) were associated with longer OS. Finally, 20% SMR was the minimum percentage associated with beneficial OS (HR 0.56; 95% CI 0.35-0.89; p = 0.01), but > 60% SMR had no significant influence (HR 0.74; 95% CI 0.45-1.21; p = 0.234).

CONCLUSIONS

SMR is associated with improved OS in patients with IDH-wt GBM who undergo GTR of CE tumor. At least 20% SMR of the CE tumor was associated with beneficial OS, but greater than 60% SMR had no significant influence on OS.

Survival impact of incidental subventricular zone irradiation in IDH-wildtype glioblastoma

BACKGROUND AND PURPOSE

The subventricular zone (SVZ) is an important niche for neural stem cells but probably also for brain tumor propagating cells, including the glioblastoma stem cell. The SVZ may become a target for radiation therapy in glioblastoma patients. However, reports studying the effect of irradiation of the SVZ on glioblastoma patient survival show conflicting results. We studied the correlation between incidental SVZ radiation dose and survival in a cohort of isocitrate dehydrogenase-wildtype (IDHwt) glioblastoma patients with inclusion of important survival prognosticators.

PATIENTS AND METHODS

In this retrospective analysis, only adult patients with supratentorial IDHwt glioblastoma were included who were treated with temozolomide-based chemoradiotherapy after surgery. The SVZ was contoured on the radiotherapy planning imaging. Cox proportional regression overall survival (OS) analysis was used to study the correlation between SVZ dose and survival. Age, Karnofsky Performance Score, extent of resection and O⁶-methylguanine-methyl-DNA-transferase gene promoter (MGMTp) methylation were used as covariates in multivariate analysis.

RESULTS

In total, 137 patients were included. Median OS was 13.3 months. The MGMTp methylation was present in 40% of cases. Ipsilateral SVZ (iSVZ) mean dose was 44.4 Gy and 27.2 Gy for the contralateral SVZ (cSVZ). Univariate survival analysis showed an inverse relationship between cSVZ mean dose and OS (HR 1.029 (1.003-1.057); p= .032). However, there was no correlation between cSVZ mean dose and OS in multivariate analysis. iSVZ dose did not correlate with survival.

CONCLUSION

In this cohort of 137 IDHwt glioblastoma patients, iSVZ did not correlate with OS. Higher cSVZ dose was inversely correlated with OS in univariate survival analysis but lost its significance in multivariate analysis, including MGMTp-methylation. Hence, the correlation between SVZ radiation and glioblastoma patient survival remains unclear. Carefully designed prospective studies are needed to provide unequivocal results on this controversial topic.

Distinguishing Pseudoprogression From True Early Progression in Isocitrate Dehydrogenase Wild-Type Glioblastoma by Interrogating Clinical, Radiological, and Molecular Features

Background: Pseudoprogression (PsP) mimics true early progression (TeP) in conventional imaging, which poses a diagnostic challenge in glioblastoma (GBM) patients who undergo standard concurrent chemoradiation (CCRT). This study aimed to investigate whether perioperative markers could distinguish and predict PsP from TeP in de novo isocitrate dehydrogenase (IDH) wild-type GBM patients.

Methods: New or progressive gadolinium-enhancing lesions that emerged within 12 weeks after CCRT were defined as early progression. Lesions that remained stable or spontaneously regressed were classified as PsP, otherwise persistently enlarged as TeP. Clinical, radiological, and molecular information were collected for further analysis. Patients in the early progression subgroup were divided into derivation and validation sets (7:3, according to operation date).

Results: Among 234 consecutive cases enrolled in this retrospective study, the incidences of PsP, TeP, and neither patterns of progression (nP) were 26.1% (61/234), 37.6% (88/234), and 36.3% (85/234), respectively. In the early progression subgroup, univariate analysis demonstrated female (OR: 2.161, P = 0.026), gross total removal (GTR) of the tumor (OR: 6.571, P < 001), located in the frontal lobe (OR: 2.561, P = 0.008), non-subventricular zone (SVZ) infringement (OR: 10.937, P < 0.001), and methylated O-6-methylguanine-DNA methyltransferase (MGMT) promoter (mMGMTp) (OR: 9.737, P < 0.001) were correlated with PsP, while GTR, non-SVZ infringement, and mMGMTp were further validated in multivariate analysis. Integrating quantitative MGMTp methylation levels from pyrosequencing, GTR, and non-SVZ infringement showed the best discriminative ability in the random forest model for derivation and validation set (AUC: 0.937, 0.911, respectively). Furthermore, a nomogram could effectively evaluate the importance of those markers in developing PsP (C-index: 0.916) and had a well-fitted calibration curve.

Conclusion: Integrating those clinical, radiological, and molecular features provided a novel and robust method to distinguish PsP from TeP, which was crucial for subsequent clinical decision making, clinical trial enrollment, and prognostic assessment. By in-depth interrogation of perioperative markers, clinicians could distinguish PsP from TeP independent from advanced imaging.

Human Cerebrospinal Fluid Modulates Pathways Promoting Glioblastoma Malignancy

Glioblastoma (GBM) is the most common and devastating primary cancer of the central nervous system in adults. High grade gliomas are able to modify and respond to the brain microenvironment. When GBM tumors infiltrate the Subventricular zone (SVZ) they have a more aggressive clinical presentation than SVZ-distal tumors. We suggest that cerebrospinal fluid (CSF) contact contributes to enhance GBM malignant characteristics in these tumors. We evaluated the impact of human CSF on GBM, performing a transcriptome analysis on human primary GBM cells exposed to CSF to measure changes in gene expression profile and their clinical relevance on disease outcome. In addition we evaluated the proliferation and migration changes of CSF-exposed GBM cells in vitro and in vivo. CSF induced transcriptomic changes in pathways promoting cell malignancy, such as apoptosis, survival, cell motility, angiogenesis, inflammation, and glucose metabolism. A genetic signature extracted from the identified transcriptional changes in response to CSF proved to be predictive of GBM patient survival using the TCGA database. Furthermore, CSF induced an increase in viability, proliferation rate, and self-renewing capacity, as well as the migratory capabilities of GBM cells in vitro. In vivo, GBM cells co-injected with human CSF generated larger and more proliferative tumors compared to controls. Taken together, these results provide direct evidence that CSF is a key player in determining tumor growth and invasion through the activation of complex gene expression patterns characteristic of a malignant phenotype. These findings have diagnostic and therapeutic implications for GBM patients. The changes induced by CSF contact might play a role in the increased malignancy of SVZ-proximal GBM.

What is the role of the subventricular zone in radiotherapy of glioblastoma patients?

BACKGROUND AND PURPOSE

Current glioblastoma (GBM) therapies prolong survival, but overall prognosis is still poor. Irradiation of the subventricular zone (SVZ) has recently been discussed as a promising concept as this tissue harbors stem cells which seem to play a role in the initiation and recurrence of GBM. In this study, we retrospectively examined the relationship of SVZ irradiation dose and survival in a large, homogeneous GBM patient cohort.

MATERIALS AND METHODS

We included 200 GBM patients who had been treated at our institution with trimodal therapy (surgery, radiotherapy and chemotherapy) between 2009 and 2020. The SVZ was delineated, and dose-volume histograms were calculated and extracted. Tumors were classified according to their contact with the SVZ. The Kaplan-Meier method was used for survival analysis, and univariable and multivariable Cox regression (MVA) were used to determine prognostic effects on progression-free survival (PFS) and overall survival (OS).

RESULTS

Median PFS of the study group was 7.2 months; median OS was 15.1 months. In MVA (with mean dose to the ipsilateral SVZ as a continuous covariable), PFS was significantly lower for patients with a Karnofsky performance status (KPS) < 70% and without MGMT promoter methylation. Factors prognostic for shorter OS were old age, lower KPS, unmethylated MGMT status, SVZ contact and biopsy instead of subtotal- or gross total resection. There was no significant correlation between survival and SVZ dose.

CONCLUSION

In this cohort, an increased mean dose to the ipsilateral or contralateral SVZ did not correlate with improved survival in irradiated GBM patients in MVA. Patients whose tumor directly involved the SVZ showed worse OS in MVA.

The Subventricular Zone, a Hideout for Adult and Pediatric High-Grade Glioma Stem Cells

Both in adult and children, high-grade gliomas (WHO grades III and IV) account for a high proportion of death due to cancer. This poor prognosis is a direct consequence of tumor recurrences occurring within few months despite a multimodal therapy consisting of a surgical resection followed by chemotherapy and radiotherapy. There is increasing evidence that glioma stem cells (GSCs) contribute to tumor recurrences. In fact, GSCs can migrate out of the tumor mass and reach the subventricular zone (SVZ), a neurogenic niche persisting after birth. Once nested in the SVZ, GSCs can escape a surgical intervention and resist to treatments. The present review will define GSCs and describe their similarities with neural stem cells, residents of the SVZ. The architectural organization of the SVZ will be described both for humans and rodents. The migratory routes taken by GSCs to reach the SVZ and the signaling pathways involved in their migration will also be described hereafter. In addition, we will debate the advantages of the microenvironment provided by the SVZ for GSCs and how this could contribute to tumor recurrences. Finally, we will discuss the clinical relevance of the SVZ in adult GBM and pediatric HGG and the therapeutic advantages of targeting that neurogenic region in both clinical situations.

A Prospective Cohort Study of Neural Progenitor Cell-Sparing Radiation Therapy Plus Temozolomide for Newly Diagnosed Patients With Glioblastoma

BACKGROUND

In treating glioblastoma, irradiation of the neural progenitor cell (NPC) niches is controversial. Lower hippocampal doses may limit neurocognitive toxicity, but higher doses to the subventricular zones (SVZ) may improve survival.

OBJECTIVE

To prospectively evaluate the impact of limiting radiation dose to the NPC niches on tumor progression, survival, and cognition in patients with glioblastoma.

METHODS

Patients with glioblastoma received resection followed by standard chemoradiation. Radiation dose to the NPC niches, including the bilateral hippocampi and SVZ, was minimized without compromising tumor coverage. The primary outcome was tumor progression in the spared NPC niches. Follow-up magnetic resonance imaging was obtained bimonthly. Neurocognitive testing was performed before treatment and at 6- and 12-mo follow-up. Cox regression evaluated predictors of overall and progression-free survival. Linear regression evaluated predictors of neurocognitive decline.

RESULTS

A total of 30 patients enrolled prospectively. The median age was 58 yr. Median mean doses to the hippocampi and SVZ were 49.1 and 41.8 gray (Gy) ipsilaterally, and 16.5 and 19.9 Gy contralaterally. Median times to death and tumor progression were 16.0 and 7.6 mo, and were not significantly different compared to a matched historical control. No patients experienced tumor progression in the spared NPC-containing regions. Overall survival was associated with neurocognitive function (P ≤ .03) but not dose to the NPC niches. Higher doses to the hippocampi and SVZ predicted greater decline in verbal memory (P ≤ .01).

CONCLUSION

In treating glioblastoma, limiting dose to the NPC niches may reduce cognitive toxicity while maintaining clinical outcomes. Further studies are needed to confirm these results.

Glioblastoma with a primitive neuroectodermal component: two cases with implications for glioblastoma cell-of-origin

BACKGROUND

Glioblastoma (GBM) is the most common primary brain malignancy, but much remains unknown about the histogenesis of these tumors. In the great majority of cases, GBM is a purely glial tumor but in rare cases the classic-appearing high-grade glioma component is admixed with regions of small round blue cells with neuronal immunophenotype, and these tumors have been defined in the WHO 2016 Classification as "glioblastoma with a primitive neuronal component."

METHODS

In this paper, we present two cases of GBM-PNC with highly divergent clinical courses, and review current theories for the GBM cell-of-origin.

RESULTS AND CONCLUSIONS

GBM-PNC likely arises from a cell type competent to give rise to glial or neuronal lineages. The thesis that GBM recapitulates to some extent normal neurodevelopmental cellular pathways is supported by molecular and clinical features of our two cases of GBM-PNC, but more work is needed to determine which cellular precursor gives rise to specific cases of GBM. GBM-PNC may have a dramatically altered clinical course compared to standard GBM and may benefit from specific lines of treatment.

Effect of conditioned medium from neural stem cells on glioma progression and its protein expression profile analysis

BACKGROUND

Emerging evidence suggests that the spread of glioma to the subventricular zone (SVZ) is closely related to glioma recurrence and patient survival. Neural stem cells (NSCs) are the main cell type in the SVZ region and exhibit tumor-homing ability.

AIM

To evaluate the effects of conditioned medium (CM) derived from SVZ NSCs on the cancer-related behaviors of glioma cells.

METHODS

The characteristics of SVZ hNSCs were identified by immunofluorescence. The normoxic-hNSC-CM and hypoxic-hNSC-CM (3% O₂, oxygen-glucose deprived [OGD] culturing) were collected from 80%-90% confluent SVZ NSCs in sterile conditions. The CCK8 and Transwell assays were used to compare and evaluate the effects of normoxic-CM and hypoxic-CM on glioma proliferation and invasion. Then proteins secreted from SVZ NSCs into the CM were investigated by mass spectrometry, and the potential effects of candidate protein NCAN in the regulation of glioma progression were examined by CCK8 and Transwell assays.

RESULTS

The CM from SVZ NSCs significantly increased the proliferation and invasion of glioma cells, particularly the CM from OGD NSCs induced under hypoxic conditions. Furthermore, the secreted protein neurocan (NCAN) in CM from OGD NSCs was identified by proteomic analysis. NCAN was expressed in glioma cells and played regulatory roles in mediating the progression of glioma cells mainly via the Rho/Rho-associated protein kinase pathway.

CONCLUSION

Our study identified a potential interactive mechanism between SVZ NSCs and glioma cells, in which SVZ NSCs promote glioma progression via the secreted protein NCAN. These findings suggested that exploring the CM derived from cells could be a novel strategy for optimizing treatments and that NCAN derived from SVZ NSCs may be a potential new target in glioma progression.

The role of radiation therapy in treatment of adults with newly diagnosed glioblastoma multiforme: a systematic review and evidence-based clinical practice guideline update

TARGET POPULATION

These recommendations apply to adult patients diagnosed with newly diagnosed glioblastoma. QUESTION 1 : In adult patients (aged 65 and under) with newly diagnosed glioblastoma, is the addition of radiation therapy (RT) more beneficial than management without RT in improving survival?

RECOMMENDATIONS

Level I: Radiation therapy (RT) is recommended for the treatment of newly diagnosed malignant glioblastoma in adults. QUESTION 2 : In adult patients (aged 65 and under) with newly diagnosed glioblastoma, is the RT regimen of 60 Gy given in 2 Gy daily fractions more beneficial than alternative regimens in providing survival benefit while minimizing toxicity?

RECOMMENDATIONS

Level I: Treatment schemes should include dosage of up to 60 Gy given in 2 Gy daily fractions that includes the enhancing area. QUESTION 3 : In adult patients (aged 65 and under) with newly diagnosed glioblastoma, is a tailored target volume superior to regional RT for reduction of radiation-induced toxicity while maintaining efficacy?

RECOMMENDATION

Level II: It is recommended that radiation therapy planning include 1-2 cm margin around the radiographically T1 weighted contrast-enhancing tumor volume or the T2 weighted abnormality on MRI. Level III: Recalculation of the radiation volume during RT treatment may be necessary to reduce the radiated volume of normal brain since the volume of surgical defect will change during the long period of RT. QUESTION 4 : In adult patients (aged 65 and under) with newly diagnosed glioblastoma, does the addition of RT of the subventricular zone to standard tumor volume treatment improve tumor control and overall survival?

RECOMMENDATION

No recommendation can be formulated as there is contradictory evidence in favor of and against intentional radiation of the subventricular zone (SVZ) QUESTION 5 : In elderly (age > 65 years) and/or frail patients with newly diagnosed glioblastoma, does the addition of RT to surgical intervention improve disease control and overall survival?

RECOMMENDATION

Level I: Radiation therapy is recommended for treatment of elderly and frail patients with newly diagnosed glioblastoma to improve overall survival. QUESTION 6 : In elderly (age > 65 years) and/or frail patients with newly diagnosed glioblastoma, does modification of RT dose and fractionation scheme from standard regimens decrease toxicity and improve disease control and survival?

RECOMMENDATION

Level II: Short RT treatment schemes are recommended in frail and elderly patients as compared to conventional 60 Gy given in 2 daily fractions because overall survival is not different while RT risk profile is better for the short RT scheme. Level II: The 40.05 Gy dose given in 15 fractions or 25 Gy dose given in 5 fractions or 34 Gy dose given in 10 fractions should be considered as appropriate doses for Short RT treatments in elderly and/or frail patients. QUESTION 7 : In adult patients with newly diagnosed glioblastoma is there advantage to delaying the initiation of RT instead of starting it 2 weeks after surgical intervention in decreasing radiation-induced toxicity and improving disease control and survival?

RECOMMENDATION

Level III: It is suggested that RT for patients with newly diagnosed GBM starts within 6 weeks of surgical intervention as compared to later times. There is insufficient evidence to recommend the optimal specific post-operative day within the 6 weeks interval to start RT for adult patients with newly diagnosed glioblastoma that have undergone surgical resection. QUESTION 8 : In adult patients with newly diagnosed supratentorial glioblastoma is Image-Modulated RT (IMRT) or similar techniques as effective as standard regional RT in providing tumor control and improve survival?

RECOMMENDATION

Level III: There is no evidence that IMRT is a better RT delivering modality when compared to conventional RT in improving overall survival in adult patients with newly diagnosed glioblastoma. Hence, IMRT should not be preferred over the Conventional RT delivery modality. QUESTION 9 : In adult patients with newly diagnosed glioblastoma does the use of radiosensitizers with RT improve the efficacy of RT as determined by disease control and overall survival?

RECOMMENDATION

Level III: Iododeoxyuridine is not recommended to be used as radiosensitizer during RT treatment for patients with newly diagnosed GBM QUESTION 10 : In adult patients with newly diagnosed glioblastoma is the use of Ultrafractionated RT superior to standard fractionation regimens in improving disease control and survival?

RECOMMENDATION

There is insufficient evidence to formulate a recommendation regarding the use of ultrafractionated RT schemes and patient population that could benefit from it. QUESTION 11 : In patients with poor prognosis with newly diagnosed glioblastoma is hypofractionated RT indicated instead of a standard fractionation regimen as measured by extent of toxicity, disease control and survival?

RECOMMENDATION

Level I: Hypofractionated RT schemes may be used for patients with poor prognosis and limited survival without compromising response. There is insufficient evidence in the literature for us to be able to recommend the optimal hypofractionated RT scheme that will confer longest overall survival and/or confer the same overall survival with less toxicities and shorter treatment time. QUESTION 12 : In adult patients with newly diagnosed glioblastoma is the addition of brachytherapy to standard fractionated RT indicated to improve disease control and survival?

RECOMMENDATION

Level I: Brachytherapy as a boost to external beam RT has not been shown to be beneficial and is not recommended in the routine management of patients with newly diagnosed GBM. QUESTION 13 : In elderly patients (> 65 year old) with newly diagnosed glioblastoma under what circumstances is accelerated hyperfractionated RT indicated instead of a standard fractionation regimen as measured by extent of toxicity, disease control and survival?

RECOMMENDATION

Level III: Accelerated Hyperfractionated RT with a total RT dose of 45 Gy or 48 Gy has been shown to shorten the treatment time without detriment in survival when compared to conventional external beam RT and should be considered as an option for treatment of elderly patients with newly diagnosed GBM. QUESTION 14 : In adult patients with newly diagnosed glioblastoma is the addition of Stereotactic Radiosurgery (SRS) boost to conventional standard fractionated RT indicated to improve disease control and survival?

RECOMMENDATION

Level I: Stereotactic Radiosurgery boost to external beam RT has not been shown to be beneficial and is not recommended in patients undergoing routine management of newly diagnosed malignant glioma.

MKP1 phosphatase is recruited by CXCL12 in glioblastoma cells and plays a role in DNA strand breaks repair

Glioblastoma (GBM) is the most frequent and aggressive primary tumor in the central nervous system. Previously, the secretion of CXCL12 in the brain subventricular zones has been shown to attract GBM cells and protect against irradiation. However, the exact molecular mechanism behind this radioprotection is still unknown. Here, we demonstrate that CXCL12 modulates the phosphorylation of MAP kinases and their regulator, the nuclear MAP kinase phosphatase 1 (MKP1). We further show that MKP1 is able to decrease GBM cell death and promote DNA repair after irradiation by regulating major apoptotic players, such as Jun-N-terminal kinase, and by stabilizing the DNA repair protein RAD51. Increases in MKP1 levels caused by different corticoid treatments should be reexamined for GBM patients, particularly during their radiotherapy sessions, in order to prevent or to delay the relapses of this tumor.

The influence of subventricular zone involvement in extent of resection and tumor growth pattern of glioblastoma

OBJECTIVES

Isocitrate dehydrogenase (IDH1/2) mutations and O6-alkylguanine DNA methyltransferase (MGMT) promoter methylations are acknowledged survival predictors in patients with glioblastoma (GB). Moreover, tumor growth patterns like multifocality and subventricular zone (SVZ) involvement seem to be associated with poorer outcomes. Here, we wanted to evaluate the influence of the SVZ involvement and the multifocal tumor growth on the extent of surgical resection and its correlation with overall survival (OS) and molecular characteristics of patients with GB.

METHODS

Adult patients with primary GB who underwent surgery at our department between 2012 and 2014 were included. Preoperative magnetic resonance imaging findings were analyzed with regard to tumor location, presence of multifocality and SVZ involvement. The extent of surgical resection as well as clinical and molecular parameters was collected from electronic patient records. Univariate and multivariate analyses were performed.

RESULTS

Two hundred eight patients were retrospectively analyzed, comprising 90 (43.3%) female individuals with a mean age of 62.9 (±12.26) years and OS of 10.2 months (±8.9). Unifocal tumor location was a predictor for better OS with a mean of 11.4 (±9.4) months (vs. 8.0 [±7.4] months, p=0.008). Affection of the SVZ was also associated with lower surgical resection rates (p<0.001). SVZ involvement revealed with 7.8 (±7.0) months a significant worse OS [vs. 13.9 (±10.1) months, p<0.001]. All six IDH1/2 wildtype tumors showed an unifocal location (p=0.066). MGMT promoter methylation was not associated with multifocal tumor growth (p=0.649) or SVZ involvement (p=0.348). Multivariate analysis confirmed independent association between the SVZ involvement and OS (p=0.001).

CONCLUSION

The involvement of the SVZ appears to have an influence on a lower resection rate of GB. This negative impact of SVZ on GB outcome might be related to lesser extent of resection, higher rates of multifocality and greater surgical morbidity but not inevitably to IDH1/2 mutation and MGMT promoter methylation status.

The Prognostic Value of MRI Subventricular Zone Involvement and Tumor Genetics in Lower Grade Gliomas

BACKGROUND AND PURPOSE

Glioblastomas (GBMs) that involve the subventricular zone (SVZ) have a poor prognosis, possibly due to recruitment of neural stem cells. The purpose of this study was to evaluate whether SVZ involvement by lower grade gliomas (LGG), WHO grade II and III, similarly predicts poorer outcomes. We further assessed whether tumor genetics and cellularity are associated with SVZ involvement and outcomes.

METHODS

Forty-five consecutive LGG patients with preoperative imaging and next generation sequencing were included in this study. Regional SVZ involvement and whole tumor apparent diffusion coefficient (ADC) values, as a measure of cellularity, were assessed on magnetic resonance imaging. Progression was determined by RANO criteria. Kaplan-Meier curves and Cox regression analyses were used to determine the hazard ratios (HR) for progression and survival.

RESULTS

Frontal, parietal, temporal, and overall SVZ involvement and ADC values were not associated with progression or survival (P ≥ .05). However, occipital SVZ involvement, seen in two patients, was associated with a higher risk of tumor progression (HR = 6.6, P = .016) and death (HR = 31.5, P = .015), CDKN2A/B mutations (P = .03), and lower ADC histogram values at the 5th (P = .026) and 10th percentiles (P = .046). Isocitrate dehydrogenase, phosphatase and tensin homolog, epidermal growth factor receptor, and cyclin-dependent kinase 4 mutations were also prognostic (P ≤ .05).

CONCLUSIONS

Unlike in GBM, overall SVZ involvement was not found to strongly predict poor prognosis in LGGs. However, occipital SVZ involvement, though uncommon, was prognostic and found to be associated with CDKN2A/B mutations and tumor hypercellularity. Further investigation into these molecular mechanisms underlying occipital SVZ involvement in larger cohorts is warranted.

Distinct topographic-anatomical patterns in primary and secondary brain tumors and their therapeutic potential

PURPOSE

Understanding the topographic-anatomical patterns of brain tumors has the potential to improve our pathophysiological understanding and may allow for anatomical tailoring of surgery and radiotherapy. This study analyzed topographic-anatomical patterns underlying neuroepithelial tumors, primary CNS lymphoma and metastases.

METHODS

Any histologically confirmed supra- or infratentorial parenchymal neoplasia of one institution over a 4-year period was included. Using high-resolution magnetic resonance imaging data, a detailed analysis of the topographic-anatomical tumor features was performed. Differences between neuroepithelial tumors, primary central nervous system lymphoma (PCNSL) and metastases were assessed using pairwise comparisons adjusted for multiple testing, upon significance of the omnibus test.

RESULTS

Based on image analysis of 648 patients-419 (65%) neuroepithelial tumors, 28 (5%) PCNSL and 201 (31%) metastases-entity-specific topographic-anatomical patterns were identified. Neuroepithelial tumors showed a radial ventriculo-cortical orientation, inconsistent with the current belief of a growth along white matter tracts, whereas the pattern in PCNSL corresponded to a growth along such. Metastases preferentially affected the cortex and subcortical white matter of large arteries' terminal supply areas. This study provides a comprehensive anatomical description of the topography of NT, PCNSL and metastases intended to serve as a topographic reference for clinicians and neuroscientists.

CONCLUSIONS

The identified distinct anatomical patterns provide evidence for a specific interaction between tumor and anatomical structures, following a pathoclitic concept. Understanding differences in their anatomical behavior has the potential to improve our pathophysiological understanding and to tailor therapy of brain tumors.

Glioblastomas located in proximity to the subventricular zone (SVZ) exhibited enrichment of gene expression profiles associated with the cancer stem cell state

INTRODUCTION

Conflicting results have been reported in the association between glioblastoma proximity to the subventricular zone (SVZ) and enrichment of cancer stem cell properties. Here, we examined this hypothesis using magnetic resonance (MR) images derived from 217 The Cancer Imaging Archive (TCIA) glioblastoma subjects.

METHODS

Pre-operative MR images were segmented automatically into contrast enhancing (CE) tumor volumes using Iterative Probabilistic Voxel Labeling (IPVL). Distances were calculated from the centroid of CE tumor volumes to the SVZ and correlated with gene expression profiles of the corresponding glioblastomas. Correlative analyses were performed between SVZ distance, gene expression patterns, and clinical survival.

RESULTS

Glioblastoma located in proximity to the SVZ showed increased mRNA expression patterns associated with the cancer stem-cell state, including CD133 (P = 0.006). Consistent with the previous observations suggesting that glioblastoma stem cells exhibit increased DNA repair capacity, glioblastomas in proximity to the SVZ also showed increased expression of DNA repair genes, including MGMT (P = 0.018). Reflecting this enhanced DNA repair capacity, the genomes of glioblastomas in SVZ proximity harbored fewer single nucleotide polymorphisms relative to those located distant to the SVZ (P = 0.003). Concordant with the notion that glioblastoma stem cells are more aggressive and refractory to therapy, patients with glioblastoma in proximity to SVZ exhibited poorer progression free and overall survival (P < 0.01).

CONCLUSION

An unbiased analysis of TCIA suggests that glioblastomas located in proximity to the SVZ exhibited mRNA expression profiles associated with stem cell properties, increased DNA repair capacity, and is associated with poor clinical survival.

Diffusion MRI changes in the anterior subventricular zone following chemoradiation in glioblastoma with posterior ventricular involvement

INTRODUCTION

There is growing evidence that the subventricular zone (SVZ) plays a key role in glioblastoma (GBM) tumorigenesis. However, little is known regarding how the SVZ, which is a harbor for adult neural stem cells, may be influenced by chemoradiation. The current diffusion-weighted imaging (DWI) study explored ipsilateral and contralateral alterations in the anterior SVZ in GBM patients with posterior enhancing lesions following chemoradiation.

METHODS

Forty GBM patients with tumor involvement in the posterior SVZ (mean age = 57 ± 10; left-hemisphere N = 25; right-hemisphere N = 15) were evaluated using DWI before and after chemoradiation. Regions-of-interest were drawn on the ipsilesional and contralesional anterior SVZ on apparent diffusion coefficient (ADC) maps for both timepoints. ADC histogram analysis was performed by modeling a bimodal, double Gaussian distribution to obtain ADC_L, defined as the mean of the lower Gaussian distribution.

RESULTS

The ipsilesional SVZ had lower ADC_L values compared to the contralesional SVZ before treatment (mean difference = 0.025 μm²/ms; P = 0.007). Following chemoradiation, these changes were no longer observed (mean difference = 0.0025 μm²/ms; P > 0.5), as ADC_L values of the ipsilesional SVZ increased (mean difference = 0.026 μm²/ms; P = 0.037). An increase in ipsilesional ADC_L was associated with shorter progression-free (P = 0.0119) and overall survival (P = 0.0265).

CONCLUSIONS

These preliminary observations suggest baseline asymmetry as well as asymmetric changes in the SVZ proximal (ipsilesional) to the tumor with respect to contralesional SVZ regions may be present in GBM, potentially implicating this region in tumorigenesis and/or treatment resistance.

Prospective study to assess the survival outcomes of planned irradiation of ipsilateral subventricular and periventricular zones in glioblastoma

Purpose/objective(s)

Retrospective evidence suggests that the irradiation of stem cells in the periventricular zone (PVZ), specifically the subventricular zone (SVZ), to higher doses may be associated with improved outcomes.

Materials/methods

This was a prospective study, done from 2012 to 2017 in glioblastoma patients to assess the efficacy of planned irradiation of ipsilateral PVZ and SVZ on survival outcomes. The clinical target volume included the tumour bed with a 1.5–2 cm margin, perilesional oedema and was expanded to encompass the ipsilateral PVZ (5 mm lateral expansion adjacent to the ventricles, including the SVZ, which was a 5 mm expansion lateral to lateral ventricle). The ipsilateral PVZ was planned to receive a dose of ≥50 Gy.

Results

89 patients were recruited of which 74 patients were available for the analysis. Median age was 48 years. Mean doses to ipsilateral PVZ and SVZ were 56.2 and 55.1Gy, respectively. Median overall survival in the entire group was 13 months. There was no significant correlation between survival and doses to ipsilateral, contralateral, or bilateral PVZ and SVZ. Median survival was 16, 12 and 6 months for Eastern Cooperative ­Oncology Group (ECOG) PS 1, 2 and 3, respectively (p = 0.05).

Conclusion

Planned irradiation of potential stem cell niches in the ipsilateral cerebral hemisphere did not result in improved survival as suggested by retrospective studies. Doses to contralateral or bilateral PVZ or SVZ also did not influence survival.

The effects of altered neurogenic microRNA levels and their involvement in the aggressiveness of periventricular glioblastoma

INTRODUCTION

Glioblastoma multiforme is the most common primary brain tumour, with the least favourable prognosis. Despite numerous studies and medical advances, it continues to be lethal, with an average life expectancy of 15 months after chemo-radiotherapy.

DEVELOPMENT

Recent research has addressed several factors associated with the diagnosis and prognosis of glioblastoma; one significant factor is tumour localisation, particularly the subventricular zone, which represents one of the most active neurogenic niches of the adult human brain. Glioblastomas in this area are generally more aggressive, resulting in unfavourable prognosis and a shorter life expectancy. Currently, the research into microRNAs (miRNA) has intensified, revealing different expression patterns under physiological and pathophysiological conditions. It has been reported that the expression levels of certain miRNAs, mainly those related to neurogenic processes, are dysregulated in oncogenic events, thus favouring gliomagenesis and greater tumour aggressiveness. This review discusses some of the most important miRNAs involved in subventricular neurogenic processes and their association with glioblastoma aggressiveness.

CONCLUSIONS

MiRNA regulation and function play an important role in the development and progression of glioblastoma; understanding the alterations of certain miRNAs involved in both differentiation and neural and glial maturation could help us to better understand the malignant characteristics of glioblastoma.

Bcl2-Expressing Quiescent Type B Neural Stem Cells in the Ventricular-Subventricular Zone Are Resistant to Concurrent Temozolomide/X-Irradiation

The ventricular-subventricular zone (V-SVZ) of the mammalian brain is a site of adult neurogenesis. Within the V-SVZ reside type B neural stem cells (NSCs) and type A neuroblasts. The V-SVZ is also a primary site for very aggressive glioblastoma (GBM). Standard-of-care therapy for GBM consists of safe maximum resection, concurrent temozolomide (TMZ), and X-irradiation (XRT), followed by adjuvant TMZ therapy. The question of how this therapy impacts neurogenesis is not well understood and is of fundamental importance as normal tissue tolerance is a limiting factor. Here, we studied the effects of concurrent TMZ/XRT followed by adjuvant TMZ on type B stem cells and type A neuroblasts of the V-SVZ in C57BL/6 mice. We found that chemoradiation induced an apoptotic response in type A neuroblasts, as marked by cleavage of caspase 3, but not in NSCs, and that A cells within the V-SVZ were repopulated given sufficient recovery time. 53BP1 foci formation and resolution was used to assess the repair of DNA double-strand breaks. Remarkably, the repair was the same in type B and type A cells. While Bax expression was the same for type A or B cells, antiapoptotic Bcl2 and Mcl1 expression was significantly greater in NSCs. Thus, the resistance of type B NSCs to TMZ/XRT appears to be due, in part, to high basal expression of antiapoptotic proteins compared with type A cells. This preclinical research, demonstrating that murine NSCs residing in the V-SVZ are tolerant of standard chemoradiation therapy, supports a dose escalation strategy for treatment of GBM. Stem Cells 2019;37:1629-1639.