Low-grade Gliomas Research Articles

TMIC-16. SPECIFIC TARGETING OF THE MRNA EXPRESSION OF TGFB2 LIGAND TO POTENTIALLY ENHANCE IMMUNE THERAPIES IN LOW-GRADE GLIOMAS

Abstract Low-grade glioma (LGG) tumors are characterized by a low infiltration of immune cells, requiring therapies augmenting the immune response in the tumor microenvironment (TME). The Transforming Growth Factor beta (TGFB) pathway contributes to an immunosuppressive environment. We propose targeting the specific inhibition of Transforming Growth Factor Beta 2, TGFB2 mRNA, as an attractive therapeutic strategy using antisense oligonucleotides. We conducted a bioinformatic-led investigation highlighting the ratio of TGFB2:TGFB1 mRNA expression levels in the cohort of 513 TCGA patients, revealing the TGFB2 ratio as a negative prognostic indicator through utilizing a multivariate Cox proportional hazards model that included the TGFB2 ratio and age at diagnosis as linear covariates to predict overall survival (OS). The model showed a 1.8-fold higher TGFB2 ratio relative to TGFB1 mRNA expression correlated to worse OS. Furthermore, the impact of the TGFB2 ratio was significantly affected by the age at diagnosis, in which older patients exhibited worse OS at increased TGFB2 ratios. Increasing the ratio of TGFB2 relative to TGFB1, TGFB3, TGFBR1, or TGFBR2 in LGG patients led to significant increases in multivariate Cox model determined hazards ratios, HR (HR (95% CI range)) of 1.372 (1.224-1.539), 1.434 (1.288-1.560), 1.327 (1.195-1.473), and 1.381 (1.233-1.547) respectively (P<0.0001 for all comparisons). Correlation of TGFB2:TGFB1/TGFB3/TGFBR1/TGFBR2 ratio across 1330 Reactome pathways using Gene Set Enrichment Analysis showed the most positively correlated genes were members of TME pathways including PD-1 signaling, Syndecan interactions, Non-integrin membrane-ECM interactions, EPH-Ephrin signaling, and Collagen biosynthesis and modifying enzymes. These results suggest that the specific targeting TGFB2 in LGG can remodel the TME for immune therapies to improve OS outcomes.

PATH-11. TECTAL GLIOMA: CLINICAL, PATHOLOGICAL, AND MOLECULAR FEATURES

Abstract Tectal glioma (TG) is a rare lower-grade glioma (LrGG) that occurs in the tectum, mainly affecting children. The clinical course is usually indolent, with common symptoms including headache, gait disturbance, and ataxia resulting from obstructive hydrocephalus. TG shares pathological similarities with pilocytic astrocytoma (PA), but recent genetic analyses have revealed distinct features, such as alterations in KRAS and BRAF. Here, we report the clinical, radiological, pathological, and molecular characteristics of TG cases in our hospital. We conducted a retrospective review of cases clinically diagnosed as TG and surgically treated at our institute between January 2005 and March 2023. Molecular analysis, including genome-wide DNA methylation profiling, was performed. Six cases were identified and the median age at diagnosis was 30.5 years (range: 6–45 years). The mean tumor diameter was 22.8 mm (range: 14.7–33.2 mm), with obstructive hydrocephalus observed in all cases. Contrast enhancement of the tumor was noted in four cases and cyst formation occurred in two cases. Four patients underwent biopsy or biopsy with endoscopic third ventriculostomy, and two patients underwent tumor resection. Postoperatively, three patients received radiotherapy and two were treated with chemotherapy. The median overall survival was 6.2 years (range: 1.4–7.3 years), and the median progression-free survival was 3.4 years (range: 1.4–7.3 years). Histological diagnoses included three cases of PA, one case of astrocytoma, and two cases of high-grade glioma. Among the three patients who underwent molecular evaluation, including genome-wide methylation analysis, two had KRAS mutation and one had H3-3A K27M mutation. Our results demonstrate the diverse histological and molecular characteristics of TG distinct from other LrGGs. Given the heterogeneous pathological background and the risk of pathological progression in TG, we emphasize the importance of comprehensive diagnosis, including molecular evaluation.

INNV-18. FOCUS ON CURRENT AND EMERGING TREATMENT OPTIONS FOR GLIOMA: A COMPREHENSIVE REVIEW

Abstract This comprehensive review delves into the current updates and challenges associated with the management of low-grade gliomas (LGG), the predominant primary tumors in the central nervous system. With a general incidence rate of 5.81 per 100000, gliomas pose a significant global concern, necessitating advancements in treatment techniques to reduce mortality and morbidity. This review places a particular focus on immunotherapies, discussing promising agents such as Zotiraciclib and Lerapolturev. Zotiraciclib, a CDK9 inhibitor, has demonstrated efficacy in glioblastoma treatment in preclinical and clinical studies, showing its potential as a therapeutic breakthrough. Lerapolturev, a viral immunotherapy, induces inflammation in glioblastoma and displays positive outcomes in both adult and pediatric patients. Exploration of immunotherapy extends to Pembrolizumab, Nivolumab, and Entrectinib, revealing the challenges and variabilities in patient responses. Despite promising preclinical data, the monoclonal antibody Depatuxizumab has proven ineffective in glioblastoma treatment, emphasizing the critical need to understand resistance mechanisms. The review also covers the success of radiation therapy in pediatric LGG, with evolving techniques, such as proton therapy, showing potential improvements in patient quality of life. Surgical treatment is discussed in the context of achieving a balance between preserving the patient’s quality of life and attaining gross total resection, with the extent of surgical resection significantly influencing the survival outcomes. In addition to advancements in cancer vaccine development, this review highlights the evolving landscape of LGG treatment, emphasizing a shift toward personalized and targeted therapies. Ongoing research is essential for refining strategies and enhancing outcomes in the management of LGG.

BIOM-01. CDKN2A HOMOZYGOUS DELETION HAS STRONGER PROGNOSTIC POWER THANIDH MUTATION IN CNS WHO GRADE 4 GLIOMAS

Abstract We conducted retrospective analysis of glioma cohorts in our institute. Medical records were reviewed for 142 glioblastoma patients for 15 years, and pathological slides were examined again for the updated diagnosis according to 2021 WHO classification of CNS tumors. The IDH mutation and CDKN2A deletion were examined by NGS analysis using ONCOaccuPanel®. Traditional prognostic factors were also examined. Mean follow-up duration was 27.5 months (ranged from 4.1 to 43.5 months) and mean overall survival (OS) was 19.4 months (95% CI 16.3 – 20.9 months). After the exclusion of 4 patients with poor status of pathologic samples, total 109 glioblastoma which were diagnosed by previous WHO criteria were changed into 26 (23.9%) astrocytoma, IDH-mutant, CNS WHO grade 4 and 83 (76.1%) glioblastoma, IDH-wildtype, CNS WHO grade 4. Among them, 61 patients (56.0%) had CDKN2A deletion. Group A was classified for 59 patients with IDH-wildtype and present CDKN2A deletion, group B was classified for 16 patients with IDH-mutant and present CDKN2A deletion, group C was classified for 48 patients with IDH-wildtype and absent CDKN2A deletion, and group D was classified for 13 patients with IDH-mutant and absent CDKN2A deletion. Group A had a mean OS of 15.70 months (95% CI 13.86 – 17.54 months), group B had a mean OS of 19.37 months (95% CI 13.43 – 25.30 months), group C had a mean OS of 22.63 months (95% CI 20.10 – 25.17 months), and group D had a mean OS of 33.38 months (95% CI 29.35 – 37.40 months). Multivariate analysis showed IDH mutation (mutant vs. wildtype; HR 6.358), and CDKN2A deletion (absence vs. presence; HR 13.452). The presenting study suggest that CDKN2A deletion should play a powerful prognostic role in CNS WHO grade 4 gliomas as well as low grade glioma. Even if CNS WHO grade 4 gliomas had mutant IDH, they can have poor clinical outcome due to CDKN2A deletion.

SURG-28. THE IMPACT OF PERILESIONAL HEATSINK STRUCTURES ON ABLATION VOLUMES AND SYMMETRY IN LASER INTERSTITIAL THERMAL THERAPY FOR THE TREATMENT OF PRIMARY CENTRAL NERVOUS SYSTEM TUMORS

Abstract BACKGROUND Laser Interstitial Thermal Therapy (LITT) has emerged as a minimally invasive treatment for primary CNS tumors. While LITT offers advantages over traditional approaches, perilesional intracranial heatsinks can lead to asymmetric ablation, impacting patient outcomes. Understanding heatsink effects is crucial for optimizing LITT efficacy. METHODS We retrospectively analyzed primary CNS tumors treated with LITT at a single tertiary care center. Ablation outcomes were quantified using the Heatsink Effect Index (HEI) measured on a scale of 0-1 (0=total symmetry; 1=complete asymmetry), and extent of ablation (EOA). Heatsink types evaluated were sulci, meninges, vasculature, and cerebrospinal fluid (CSF) spaces, inclusive of ventricles, surgical resection cavities, and CSF cisterns. Statistical analyses assessed the relationship between heatsink proximity and ablation outcomes. RESULTS A total of 99 patients satisfied all selection criteria. The cohort was 53% female, with a mean age of 61 years. Glioblastoma was the most predominant tumor type (78%), followed by low grade gliomas (15%), and meningiomas (4%). Heatsink proximity significantly correlated with ablation asymmetry (HEI) (p < 0.001), particularly at the midpoint of the catheter trajectory. The correlation between closest heatsink distance and HEI varied across the different heatsink types, with distance to vasculature and CSF spaces correlating the strongest with ablation asymmetry. When assessing the relationship between EOA and medial HEI during suboptimal ablations (EOA < 100%), we demonstrated a negative correlation showing improved EOA as HEI was reduced. Optimal cutoff catheter-heatsink distances for predicting ablation asymmetry ranged from 6.6-13.0 mm, emphasizing the impact of heatsink proximity on LITT efficacy. CONCLUSION We show that proximity to heatsinks, especially within a threshold distance of 13.0mm from the laser catheter, significantly predicts ablation asymmetry and volume in the setting of primary CNS tumors. Neurosurgeons should consider heatsink effects in pre- and intraoperative planning to optimize LITT outcomes and preserve normal brain tissue.

CSIG-01. DECREASING EXPRESSION OF TRAF PROTEINS WITH INCREASING MALIGNANCY WITH LOWEST EXPRESSION IN IDH-WILDTYP GLIOBLASTOMA

Abstract The tumor necrosis factor receptor-associated factors (TRAF) are cytoplasmatic adapter proteins that can interact directly with the intracellular domains of cell surface receptors, such as the TNF receptor superfamily. TRAFs are thus involved in cellular processes like proliferation or apoptosis. Seven members are known; all expressed in the cytosol of various cell and tissue types. Increased levels of TRAF4 in GBM tissue are related to cell proliferation and migration. About 25 % of grade I meningioma show mutations in TRAF7, which are associated with a lower risk of malignant transformation. Therefore expression patterns of all seven TRAF members are evaluated in different glioma grades. Following tumor samples were obtained during neurosurgery and shock frozen in liquid nitrogen: peritumoral tissue, astrocytoma and oligodendroglioma (G2, G3) and glioblastoma (primary and recurrent). Transcription rate of TRAF1-7 was measured via qPCR. Correlation of TRAF expression level and patient overall survival was evaluated using TCGA datasets of the TCGA-LGG” and “TCGA-GBM” projects. With the exception of TRAF5, a decreased mRNA level with increasing malignancy could be found for all TRAFs (TRAF1 p=n.s.; TRAF2 p=0.0026; TRAF3 p<0.0001; TRAF4 p=0.0021; TRAF6 p<0.0001; TRAF7 p<0.0001). IDHwt glioblastoma showed significant lower expression level compared to IDHmut glioblstoma in all TRAFs except for TRAF1 (TRAF2 p<0.0001; TRAF3 p=0.0346; TRAF4 p<0.0001; TRAF6 p=0.0447; TRAF7 p=0.0081). TRAF5 again showed a reverse effect (p=0.0065). Correlation of TRAF expression level in low grade glioma and patient survival revealed longer overall survival with low TRAF1,2,4 and TRAF5 expression (p<0.0001, p= 0.0178, p=0.0307, p<0.0001). No difference in survival rate in high grade glioma could be found.

CNSC-06. NAVIGATING BRAIN CANCER: PATIENT STORIES AND MEDICAL BREAKTHROUGH

Abstract The complex interplay of genetic mutation, dys regulated signalling pathways, Epigenetic modifications and Interaction with tumor microenvironment are the major aggravating factors for Brain Tumors. Neurological complications involve Increased Intracranial pressure, Seizures, Motor and Sensory deficits, Aphasia, Hydrocephaly, Behavioral and personality changes, Cerebellar Symptoms. It is diagnosed in a sequential steps. Collecting good history from patient in primary then examining the patient all through and making some investigations to come to a final diagnosis. On asking history to a patient he complains of recurrent convulsions, Personality changes and some motor activity deficit and loss of few senses. On examination we can reveal defect in cranial nerve functions, Motor or sensory deficits, loss of reflexes and coordination. Then Investigations being the next step for diagnosis, We ask the patient to undergo for a test for Blood Biomarkers and CSF analysis in case of suspection of metastatic Brain tumors. Biopsy to obtain for Histopathological Examination. Histopathological examination is done for analysis of genetic mutations and molecular markers. The other imaging techniques like MRI, MRS, CT, PET, EEG are done. This gives a clear picture of what actually caused tumor and shows a way for treatment. Now the treatment involves both Medical and Surgical treatment. Medical treatment includes Chemotherapy along with radiation therapy where the drugs given are Temozolomide and targeted therapy included EGFR BRAF inhibitors for glioblastoma and low grade gliomas respectively. Tumor treating fields- Optune is given. Surgical treatment involves Craniotomy for removal of primary Brain tumors, Neuro Endoscopy if tumor is present in ventricles or base of Brain, Laser interstitial Thermal therapy for deap seated and recurrent brain tumors. This is all about the treatment and now the patient management is very important for further clinical help. Physical, occupational and speech therapy helps patients recover. Symptomatic approach for inoperable tumors Provide comprehensive support for patients nearing end of life, Emphasise confidence and Quality of life.

SURG-23. ESTABLISHMENT OF AN APPROPRIATE GLIOMA SURGERY SYSTEM CONSIDERING MOLECULAR AND FUNCTIONAL BOUNDARIES

Abstract Gliomas are invasive tumors and cannot be cured by surgery. But surgical removal has also been proven to affect treatment outcomes. Recent advances in molecular diagnostics have identified IDH mutations, especially in lower grade gliomas, allowing the identification of so-called molecular boundaries. It is conceivable that expanded resection to the molecular border may improve treatment outcome. On the other hand, extended resection may be incompatible with functional preservation. In such cases, it is also important to consider that the impact of surgery on treatment outcome has also been proven to vary by glioma genotype. While total resection has a significant prognostic impact on survival in astrocytomas with IDH mutations, the impact on survival in oligodendrogliomas that are sensitive to chemoradiotherapy and, conversely, in high-grade tumors without IDH mutations is lower than in the former. Therefore, it is important to determine the extent of removal after considering the tumor type. In general, various surgical support devices such as surgical navigation systems, fluorescent diagnosis using 5ALA, intraoperative electrophysiological monitoring, awake functional brain mapping, and intraoperative MRI are applied during glioma surgery. In addition to these, we have developed a surgical system that also focuses on tumor subtypes by introducing preoperative tumor type prediction using AI imaging and intraoperative rapid genetic diagnosis. We have further developed intraoperative rapid genetic diagnosis to identify genetic mutations around the tumor, enabling the detection of molecular boundaries. It is now possible to remove as much as possible, considering the molecular boundary, while paying sufficient attention to preservation of brain functions. Gliomas are intractable diseases, but their treatment outcomes have steadily improved over time. We are now in an era of a tailor-made surgery based on a variety of data. Implementing “appropriate surgical procedures” we aim at further improvement of treatment outcomes.

NCMP-19. IMPACT OF SUBVENTRICULAR ZONE INVASION ON PREOPERATIVE COGNITIVE DECLINE IN DIFFUSE GLIOMA PATIENTS

Abstract PURPOSE To determine the impact of subventricular zone (SVZ) invasion on neurocognitive dysfunction in diffuse glioma patients. MATERIALS AND METHODS We collected neuropsychological assessments of treatment-naïve WHO grade 2-4 diffuse glioma patients between 2017 to 2023. The Chi-square test determined the odds ratio (OR), and multiple linear regression identified factors related to cognitive deficits using Python 3.11.4. RESULTS Of the 129 patients, 64 exhibited SVZ invasion (SVZ+) while 65 were SVZ-. Groups were matched for WHO grading. SVZ+ was associated with more defective domains than SVZ- in both lower grade (WHO grade 2,3, 3.2 ± 2.1 vs. 2.1 ± 1.9, p=0.019) and high grade (WHO grade 4, 4.9 ± 1.6 vs. 3.6 ± 2.2, p=0.019) tumors. In lower grade gliomas, SVZ+ increased risks of language (OR 7.500, p<0.001) and visual learning impairments (OR 4.375, p=0.014). In high grade gliomas, SVZ+ rendered greater language (OR 8.556, p=0.003) and auditory learning vulnerability (OR 3.850, p=0.039). In right hemispheric tumors, SVZ+ lesions conferred worse executive (OR 6.667, p=0.006) and language function (OR 9.063, p=0.017); in left hemispheric tumors, SVZ+ lesions increased language (OR 3.125, p=0.012) and auditory learning (OR 2.889, p=0.024) impairment. Frontal horn of SVZ+ was related to working memory decline, and body part of SVZ+ was related to emotional deficits. Age and WHO grade 4 were associate with more defective domains in the SVZ+ group. In the SVZ- group, parietal lobe tumor was associate with more defective domains, while high education, temporal lobe, and WHO grade 2 were associate with fewer defective domains. CONCLUSION SVZ invasion impacts pre-operative neurocognitive function regardless of lesion laterality and WHO grade. Distinct SVZ sub-regions are linked to specific cognitive impairments. These findings highlight the need for precise tumor mapping involving the SVZ to evaluate neurocognitive outcomes and consider preventive or rehabilitative interventions.

NIMG-22. QUANTITATIVE BRIGHTNESS ANALYSIS OF 5-ALA FLUORESCENCE IN GLIOMA SURGERY

Abstract OBJECTIVE The 5 aminolevulinic acid (5-ALA) is used for intraoperative tumor visualization in neurosurgery. We hypothesized that glioma may vary in pathology according to the brightness of 5-ALA fluorescence, which we quantified and compared with the pathological results of glioma. METHODS From 2019 to 2023, we investigated 28 glioma patients who underwent surgery with 5-ALA. The pathological diagnosis was based on classification of WHO 2016. The 5-ALA was administered before surgery, and the brightness of 5-ALA fluorescence was quantified. RESULTS Seventeen cases of glioblastoma (GBM), four cases of anaplastic astrocytoma (AA), three cases of oligodendroglioma (OL), and four cases of low grade glioma (LGG) were examined. The mean (SD) brightness of 5-ALA fluorescence was 155.9 (56.0) in GBM, 180.5 (64.7) in AA, and 66.3 (18.8) in OL. The brightness in OL was significantly lower than that in GBM and AA (Scheffe’s test, p<0.05). All LGGs showed negative in the brightness. CONCLUSIONS The brightness of 5-ALA fluorescence was shown to vary by pathology, which may contribute to intraoperative diagnostic support.

NCOG-04. MEMORY TRACT SPARING USING DIFFUSE TENSOR IMAGING IN RADIATION PLANNING OF PRIMARY BRAIN TUMORS

Abstract INTRODUCTION Radiation therapy (RT) is a critical treatment modality for both primary and metastatic brain tumors, yet approximately 30% of patients experience cognitive decline post-radiotherapy. This cognitive toxicity is linked to low radiation doses affecting neural stem cells in the hippocampal dentate gyrus. Hippocampal Avoidance (HA)-Whole Brain Radiotherapy (WBRT) combined with Memantine has shown promising outcomes in preserving cognitive function and quality of life (QOL) in patients with brain metastases, suggesting it should be the standard of care for those with good performance status and no hippocampal metastases. METHODS We conducted a prospective trial approved by the IRB (SMC0307-23), including patients aged 18 and above with primary brain tumors post-resection or biopsy. Exclusion criteria included multifocal glioma crossing to the other hemisphere. RT was delivered to a total dose of 60Gy in 30 fractions with concomitant TMZ. Diffusion tensor imaging (DTI) was performed to map hippocampal-associated white matter tracts. Memory fiber tracts and hippocampi were contoured and integrated into RT planning using Eclipse treatment planning software. Dosimetric analyses compared two plans: one with memory fiber constraints and one without. RESULTS Twelve patients with low-grade gliomas were included, with successful contouring of memory fibers and hippocampi. VMAT treatment plans met dose constraints for memory fibers, with an average mean dose of 10.1 Gy. The average MoCA score before RT was 27.1 and 26.4 at six months post-treatment, with a p-value of 0.07. Excluding one patient, the scores were 27.1 and 26.6, respectively (p=0.13). CONCLUSION MRI planning using DTI for memory fiber detection and incorporation into RT planning via VMAT techniques enables hippocampal and associated white fiber sparing, potentially preserving cognitive function. Preliminary cognitive data are promising, supporting the need for further validation in a larger cohort.

INNV-10. ULTRA-RAPID INTRAOPERATIVE GLIOMA TUMOR CELL QUANTIFICATION

Abstract The diagnosis and treatment of brain tumors often depends on molecular-genetic data. To date, however, there has been no intraoperative method to rapidly and iteratively utilize tumor-specific genetic alterations to guide brain tumor surgical resections, complicating intraoperative diagnosis and precluding measurement of tumor cell burdens at surgical margins. To address this gap, we developed Ultra-Rapid droplet digital PCR (UR-ddPCR), which can be completed in 15 minutes from tissue to result with an accuracy and sensitivity comparable to standard ddPCR. We demonstrate an UR-ddPCR assay for the IDH1 R132H clonal mutation that is present in many low-grade gliomas. We illustrate the clinical feasibility of UR-ddPCR by performing it intraoperatively for 49 samples from 13 glioma cases, achieving intraoperative quantification in an average of 14 minutes and 54 seconds spanning a wide dynamic range from 0.1% to 94% tumor cell percentages. We further combine UR-ddPCR measurements with UR-stimulated Raman histology intraoperatively to estimate tumor cell densities in addition to tumor cell percentages, across a wide range from < 1 to 1332 cells/mm2. We anticipate that UR-ddPCR, along with future refinements in assay instrumentation, will enable novel point-of-care diagnostics and the development of molecularly-guided brain tumor surgeries that improve clinical outcomes.

CNSC-43. NEUROTRANSMITTER DEPENDENCY UNDERLIES TUMOR GROWTH IN HUMANIZED PEDIATRIC LOW-GRADE GLIOMA MODELS

Abstract Brain tumors arise in close association with neurons, suggesting that these non-neoplastic cells may be critical stromal drivers of brain tumor initiation and growth. Previously, we have shown that murine low-grade optic glioma formation and progression in the setting of Neurofibromatosis type 1 (NF1) is dictated by neurons and neuronal activity. In these studies, these neuronal dependencies reflected neuronal activity-driven enzymatic cleavage of a growth factor (neuroligin-3) from oligodendrocyte precursors cells (tumor initiation) or neuronal production of a paracrine factor to stimulate T cell support of optic glioma growth (tumor progression). Since neurons typically communicate with other neurons through neurotransmitters, we sought to explore the possibility that neurotransmitters operate to modulate low-grade glioma growth using humanized mouse models of pilocytic astrocytoma (PA). Leveraging single cell RNA sequencing of three independent sets of pediatric PAs, we identified neurotransmitter pathway enrichment in the tumor cells. This neurotransmitter pathway enrichment reflected aberrant expression of specific neurotransmitter receptors, which we confirmed in three independently generated PA tissue microarrays and in five distinct primary PA cell lines grown in vitro. Moreover, this aberrant neurotransmitter receptor expression established differential neurotransmitter PA growth dependencies in vitro. Importantly, interruption of neurotransmitter signaling in human PA xenografts attenuated tumor growth and ERK activation in Rag1-/- mice in vivo. Finally, we discovered crosstalk between neurotransmitter receptor and receptor tyrosine kinase signaling that revealed another target for therapeutic inhibition. Taken together, these findings elucidate a previously unknown neurotransmitter PA growth dependency amenable to therapeutic targeting.

DDDR-12. INHIBITION OF NOTCH PATHWAY VIA A NOVEL MONOCLONAL ANTIBODY PROLONGS SURVIVAL IN HIGH GRADE GLIOMA MODELS

Abstract High grade gliomas (HGGs) have poor prognosis partially owing to a glioma-stem cell (GSC) population that escapes most therapeutic modalities. Inhibition of NOTCH signaling, necessary for GSC maintenance, has shown promise, however clinically limited by systemic (on-target, off-tumor) side effects. Thus, we develop a novel monoclonal antibody, 1H5, inhibitory against a disintegrin and metalloproteinase 10 (ADAM10), a protein responsible for NOTCH signaling initiation in tumor tissue, to treat HGGs. Patient-derived, glioma cell lines were treated with 1H5 to determine therapeutic IC50 and characterize downstream, NOTCH-related effectors. A patient-derived explant system, which best replicates the tumor microenvironment in vitro, was generated and treated. An orthotopic xenograft model (PDX) of HGG was created and treated with convection enhanced delivery (CED) of 1H5 to assess tumor volume and survival. We determined that ADAM10 is found in a majority of IDH-wildtype HGGs, but not on IDH-mutant HGGs or low-grade gliomas. 1H5 has nanomolar IC50 against a large library of HGG patient-derived cell lines, achieving cell death via NOTCH-signaling inhibition. In explants, treatment with 1H5 significant delays explant progression (p = 0.01), expansion (4.1-fold decrease, p = 0.007), and reduces the fraction of ADAM10+ cells (from 63.3% to 2.6%, p = 0.004), of replicating cells (from 10.0% to 0.9%, p = 0.006), and of GSCs (SOX2+ cells; from 65.8% to 12.8%, p = 0.06). In vivo, CED of 1H5 both slows down tumor growth compared to vehicle-treated controls (2.2-fold decrease in tumor volume, p = 0.03), and significantly prolongs survival (p = 0.01), without the development of significant side effects, through a reduction of replicating cells (p = 0.01) and SOX2+ GSCs (p < 0.0001), in a dose-dependent fashion. In conclusion, 1H5 is efficacious against HGG preclinical models both in vitro and in vivo by targeting NOTCH signaling. This posits 1H5 as a new promising therapeutic worthy of expeditious clinical translation.

CTNI-07. LONG-TERM EFFICACY AND SAFETY OF LAROTRECTINIB IN PATIENTS WITH TRK FUSION PRIMARY CENTRAL NERVOUS SYSTEM (CNS) TUMORS: AN UPDATED ANALYSIS

Abstract BACKGROUND Larotrectinib is a highly selective TRK inhibitor approved for TRK fusion tumor-agnostic use. We report updated data on larotrectinib-treated patients with TRK fusion primary CNS tumors. METHODS Patients enrolled in 2 clinical trials (NCT02637687 [SCOUT], NCT02576431 [NAVIGATE]) were included. Responses were independent review committee (IRC)-assessed (RANO). Patients from SCOUT could stop larotrectinib in the absence of on-treatment progression (wait-and-see). Data cutoff: July 2023. RESULTS Fifty-five patients (38 aged <18 years at enrolment) were evaluated, including 16 with non-measurable disease at baseline. Tumor histologic groups included: high-grade glioma (HGG; n=32), low-grade glioma (LGG; n=15), and other (n=8). For all patients (n=55), ORR was 27% (95% CI 16-41): 3 CR, 12 PR, 24 SD (15 for >24 weeks), 12 PD, and 4 not evaluable. For pediatric patients (n=38), ORR was 37% (95% CI 22-54). ORR in patients with measurable disease only was 38% (95% CI 23-55) for all patients (n=39) and 52% (95% CI 32-71) for pediatric patients (n=27). The 24-week disease control rates were 55% (95% CI 41-68) and 74% (95% CI 57-87) for all patients and pediatric patients, respectively. Median time to response, DoR, PFS, and OS were 2, 12 (95% CI 6-not estimable [NE]), 12 (95% CI 7-20), and 38 months (95% CI 23-NE), respectively. Treatment duration ranged from 1 to 64+ months. At data cutoff, 1 pediatric patient with HGG and 4 with LGG entered wait-and-see; median duration of first wait-and-see period was 20 months (range 4-29). One pediatric patient with LGG resumed treatment following disease progression in wait-and-see. Treatment-related adverse events were predominantly Grade 1/2. CONCLUSION Larotrectinib demonstrated rapid, durable responses and manageable safety in patients with TRK fusion primary CNS tumors. This supports the adoption of NGS panels containing NTRK gene fusions when testing patients to identify those who might benefit from TRK inhibitor therapy.

EXTH-08. IVOSIDENIB THERAPY FOR IDH-MUTANT WHO GRADE 4 ASTROCYTOMA

Abstract BACKGROUND Isocitrate Dehydrogenase (IDH) is a commonly mutated gene in gliomas, present in approximately 10% of high-grade gliomas. Its oncometabolite, D-2-hydroxyglutarate, has been implicated in promoting gliomagenesis and epileptogenesis. IDH-1 or IDH-2 mutations confer a more favorable prognosis in gliomas than wildtype IDH, leading to the differentiation between IDH-wild type glioblastoma and IDH-mutant WHO Grade 4 astrocytoma. Although IDH-mutant WHO Grade 4 astrocytomas tend to occur in younger patients and show an improved survival, prognosis remains poor and treatment options are limited. Ivosidenib is a small molecule inhibitor of IDH-1 that has shown promise for treating low-grade IDH-mutant glioma. However, little is known about its efficacy in IDH-mutant WHO Grade 4 astrocytoma. METHODS We present a retrospective case of a 38-year-old male with a WHO Grade 4 astrocytoma. Molecular characterization revealed that it was IDH-mutant, MGMTp methylated, and 1p/19q co-deleted. It was treated with ivosidenib at second recurrence. He was originally treated with gross total resection, followed by radiation and 6 cycles of adjuvant temozolomide. At the time of 1st progression (approximately 19 months postoperatively), he was treated with lomustine at 90mg/m2 but progressed after 2 cycles. Here we report the effects of off label use of ivosidenib. RESULTS Radiological surveillance showed interval decrease in tumor size starting two months after initiation of ivosidenib. The patient remained neurologically intact and no adverse effects were observed. A review of the literature revealed only three studies analyzing the effects of ivosidenib in IDH-mutated WHO Grade 4 astrocytomas with varying results. CONCLUSION The INDIGO trial published last year showed evidence of efficacy in using an IDH inhibitor for low-grade gliomas. The role of these drugs in high-grade IDH-mutated gliomas is currently unknown. Further studies are needed to assess their efficacy in overall and progression free survival, specifically in IDH-mutated WHO Grade 4 astrocytoma.

PATH-20. CLINICAL FINDINGS AND PROGNOSIS OF ADULT GLIOBLASTOMA HARBORING ABRAF V600E MUTATION

Abstract BACKGROUND AND AIM Although the BRAF V600E mutation is commonly associated with pediatric low-grade gliomas, glioblastomas (GB) with this mutation (BRAF-GB) have also been reported. The recent emergence of RAF and MEK inhibitors for BRAF V600E-positive tumors highlights the potential for targeted therapy in a subset of GB patients. This study aimed to characterize the clinical features and prognosis of BRAF-mutant glioblastomas. MATERIALS AND METHODS A retrospective analysis was conducted on a cohort of patients diagnosed with GB (confirmed by 2021 WHO criteria) above 16 years of age. Targeted genetic analysis for mutations in BRAF V600E, TERT promoter, and CDKN2A/B was performed on the GB samples. Clinical features of BRAF-GB were analyzed, and patients were further categorized into three groups: BRAF-GB, typical GB, and molecular GB. Subsequent analysis compared the prognosis among these groups. RESULTS Our study identified 11 cases (5.1%) harboring the BRAF V600E mutation among 215 adult GB patients. Patients with BRAF-GB exhibited a significantly younger median age of onset (38-year-old) compared to the typical GB (N = 167, 64-year-old) and molecular GB (N = 37, 61-year-old) groups. Further analysis of the BRAF-GB cohort (n=11) revealed a high prevalence (82%) of homozygous CDKN2A/B deletions, and only one case (9%) harbored a TERT promoter mutation. Interestingly, three BRAF-GB patients presented with hemorrhagic onset. Four cases showed evidence of prior lesions, with one case diagnosed histologically as a low-grade glioma 14 years earlier. The BRAF-GB group exhibited significantly longer median progression-free survival (32.8 months) and overall survival (84.2 months) compared to both the typical GB group (9.6 months and 18.9 months, respectively) and the molecular GB group (14.1 months and 32.1 months, respectively). CONCLUSIONS Early-age onset, with hemorrhagic onset or presence of prior lesions are factors that could lead to recommendation of BRAF analysis for adult GB patients.

CTNI-47. A PHASE 1, RANDOMIZED, PERIOPERATIVE TRIAL OF VORASIDENIB AND IVOSIDENIB IN IDH1-MUTANT DIFFUSE GLIOMA: UPDATED RESULTS

Abstract BACKGROUND Vorasidenib (VOR) and ivosidenib (IVO) showed clinical activity in subjects with isocitrate dehydrogenase mutant (mIDH) gliomas. We evaluated both agents in a phase 1, randomized, open-label perioperative trial (NCT03343197). Pharmacodynamics, pharmacokinetics, and preliminary objective response rate (ORR) data as of 29-April-2020 were previously reported (Mellinghoff et al. Nat Med. 2023). Progression-free survival (PFS) data were not mature at publication time. We report here longer-term follow-up results, including mature PFS. METHODS Participants with grade 2/3 non-enhancing mIDH1 R132H mutant gliomas were randomized to VOR (50 or 10 mg QD), IVO (500 or 250 mg BID), or no treatment (control) for 4 weeks prior to planned surgery, with the option to continue treatment with VOR or IVO post-surgery. Secondary objectives included PFS, ORR assessed by Investigator in the post-surgery period, and safety profile of VOR and IVO. RESULTS Enrollment completed in April-2019. 49 participants were randomized, of which 46 participants (24 oligodendroglioma, 20 astrocytoma, 1 anaplastic oligodendroglioma, 1 anaplastic oligoastrocytoma) received treatment with either VOR (N=24) or IVO (N=22) after surgery. As of 23-September-2023 data cutoff, 11 (46%) and 5 (20%) participants remain on treatment for VOR and IVO, respectively. Median (range) post-operative treatment duration was 44.7 months (0.9–62.7) for VOR, 23.9 months (0–62.7) for IVO. Median (95% CI) PFS was 41.4 months (9.3, NE) for VOR and 38.6 months (18.3, NE) for IVO. ORR per Response Assessment in Neuro-Oncology in low-grade gliomas (RANO-LGG) was 46% for VOR and 27% for IVO. Longer safety follow up will also be presented. CONCLUSION These results provide further evidence of prolonged response using IVO and VOR immediately following surgery in predominantly non-enhancing gliomas. This longer-term follow-up is consistent with Phase 3 INDIGO study results where VOR demonstrated PFS benefit with manageable safety compared with placebo in participants with non-enhancing mIDH gliomas.

TMOD-20. RAPID PROCESSING AND BIOBANKING OF RESECTED BRAIN TUMOR TISSUE TO GENERATE PATIENT-DERIVED BRAIN TUMOR EXPLANT ORGANOIDS (GBOS) FOR PRECLINICAL STUDIES

Abstract Improved preclinical tools are urgently needed to translate new brain cancer treatments. Patient-derived brain tumor explant organoids (GBOs) offer promise for studying tumor cells in a relevant human tumor microenvironment and predicting patient responses to therapy. However, generating GBOs is time-consuming, costly, and technically challenging, hindering the creation of comprehensive biobanks covering the spectrum of brain tumor heterogeneity. This work presents a semi-automated method for producing GBOs, involving tumor tissue processing, size selection, and same-day cryopreservation, reducing generation time to less than 1 hour. We established a biobank of 24 GBOs from 33 samples (11 males and 13 females) with primary (n=13, GBO Yield (GY)>90%) and recurrent (n=5, GY>90%) glioblastomas, high-grade gliomas (HGG, n=2, GY≤50%), and low-grade gliomas (LGG, n=2 with GY>90%, n=2 with GY≤50%). Using GBO size and propidium iodide as readouts, we used this biobank to compare anticancer activities of novel idronoxil-conjugated benzopyran compounds (NX786, NX904/904E1) against Bortezomib (100% cell death reference). NX786 and NX904/904E1 reduced GBO growth (≥50%) in all primary glioblastoma and one (of two) recurrent glioblastoma GBOs with milder effects in LGG GBOs. Two (of four) primary glioblastoma, one (of two) recurrent glioblastoma, and one LGG GBOs exhibited significant cell death (>60%) in response to NX904/904E1. In contrast, NX786 induced cell death in one (of three) primary glioblastoma (34% cell death) and one (of two) recurrent glioblastoma (71% cell death) GBOs but not in LGG GBOs, together showcasing varied responses across different brain tumors. Highly-passaged GBOs lacking the non-malignant tumor microenvironment were more susceptible to these treatments, underlining the tumor microenvironment’s critical role in responses to anticancer agents. We provide a new method for efficient processing and cryopreserving GBOs, enabling the establishment of large biobanks for patient-specific preclinical drug testing across brain tumor subgroups in a clinically relevant human 3D model.

TMIC-15. GUT MICROBIOTA CONTROLS NEUROFIBROMATOSIS-1 (NF1) OPTIC GLIOMA GROWTH THROUGH IMMUNE CIRCUIT MODULATION

Abstract Changes in the gut microbiome can have profound effects on the nervous system through modulation of T cell and microglia function. Since our prior studies demonstrated that T cells and microglia positively regulate low-grade glioma growth through the establishment of T cell-microglia immune circuit, we sought to explore the impact of changes in the gut microbiota on tumor biology. For these studies, genetically engineered Neurofibromatosis type 1 (NF1) optic glioma (Nf1-OPG) mice were raised in a germ-free environment or treated with antibiotics to deplete gut bacteria. First, we demonstrated that Nf1-OPG mice raised in a germ-free (gnotobiotic) environment or treated with specific antibiotics lacked optic gliomas and had improved OPG-induced retinal pathology (increased retinal nerve fiber layer thickness). Second, germ-free and antibiotic-treated Nf1-OPG mice gavaged with fecal microbiota from Nf1-OPG mice raised in a standard barrier facility restored optic glioma growth. Third, we showed that both germ-free and antibiotic-treated Nf1-OPG mice exhibited reduced intra-tumoral CD8+ T cell content resulting from decreased microglia chemokine production. Fourth, we discovered a gut-brain paracrine axis whose interruption reduced optic glioma growth and attenuated retinal nerve fiber layer thinning. Collectively, these findings establish a mechanistic relationship between the gut microbiota and brain tumor growth relevant to potential therapeutic interventions for pediatric low-grade gliomas.