Central Nervous System Tumors Research Articles

Giant cerebellar neurocysticercosis masquerading a primary central nervous system neoplasm – A case report with review of literature

Background: Neurocysticercosis (NCC) is one of the leading parasitic infections of the brain. Giant NCC is rare, with only two cases of cerebellar involvement reported till now. In the presence of a host immune response, these giant NCCs can mimic primary central nervous system neoplasms. The objective of this article is to report a rare case of giant cerebellar NCC and its management strategy with a literature review. Case Description: A young male presented with a giant cerebellar ring-enhancing mass with features of raised intracranial pressure, and surgical excision was done. The patient made an uneventful recovery. Conclusion: Surgical excision is safe for NCC, especially in the presence of a diagnostic dilemma.

Real-time intraoperative ultrasound imaging of the posterior pituitary gland during endoscopic endonasal approach.

Pituitary adenomas are amongst the most common benign central nervous system tumors, and often require resection via an endoscopic endonasal approach (EEA). Two of the most common associated complications are central diabetes insipidus (DI) and syndrome of inappropriate antidiuretic hormone secretion (SIADH). Both are thought to be caused by manipulation of the posterior pituitary gland (PPG), making intraoperative visualization and preservation of this structure critical. Intraoperative endoscopic endonasal ultrasound (IEUS) may present an optimal tool for this purpose. This study aims to describe the appearance and morphology of the PPG on IEUS. This study included all pituitary adenoma surgeries during which IEUS was utilized and the PPG was visualized between 1/1/2022, and 12/31/2023. Demographic, clinical, pathological, and radiological data were retrospectively collected. The PPG was described as either hypoechoic, isoechoic, or hyperechoic as compared to the anterior pituitary gland and adenoma, and the morphology of the PPG was further classified as ellipse or crescent shaped. The PPG was hypoechoic in all 43 cases included in our final cohort (100.0%). Morphologically, the PPG appeared elliptical in 27 cases (62.8%), and crescent shaped in 16 cases (37.2%). The PPG can typically be visualized by IEUS as a hypoechoic structure immediately anterior to the posterior wall of the sella turcica, with elliptical morphology being the most common appearance. These characteristics can be used by the skull base surgeon to more confidently identify the position and morphology of the PPG intraoperatively for its' preservation.

MANAGEMENT OF EXTRAMEDULLARY INTRADURAL SPINAL TUMORS

Spinal tumors are relatively uncommon, accounting for approximately 5%–10% of all central nervous system tumors, with an estimated 70%–80% being located in the intradural extramedullary space. The most common intradural extramedullary tumors are schwannomas, followed by meningiomas. Other less common intradural extramedullary tumors include myxopapillary ependymomas. The clinical presentation of these tumors is often rather nonspecific, and clinicians must maintain a high index of suspicion when evaluating patients with chronic back pain. Approximately 50% of affected individuals experience nonspecific back pain, whereas radiating pain, motor deficits, and sensory loss often progress gradually. This study examines the surgical management of intradural spinal tumors treated in our department, focusing on surgical techniques Some of these benign lesions can pose a surgical challenge due to their location to spinal cord, tumor consistency (densely mineralized / calcified). Posterior approaches involving laminectomy while preserving facet joints are typically sufficient for the surgical resection of dorsal and dorsolateral tumors. In conclusion the total surgical removal of these tumors while preserving neurological function remains can pose a surgical challenge especially for those that are densely calcifed and situated anterolateral to spinal cord, but employing standard microsurgical techniques often makes these resections possible.

Abstract B012: M-PACT: Methylation-based predictive algorithm for CNS tumor liquid biopsies

Abstract Background: DNA methylation-based classification has been transformative in the molecular diagnostics of pediatric central nervous system (CNS) tumors. Current diagnostic pipelines integrate histopathology and molecular tools in accordance with the WHO classification of CNS tumors which rely on the availability of tissue specimens. However, some tumors are not amenable to neurosurgical resection due to their high-risk locations and tissue collection is not routinely performed at relapse. In addition, molecular biomarkers are largely lacking for longitudinal disease monitoring in pediatric neuro-oncology. Liquid biopsies (LBs) have emerged as a minimally invasive, longitudinal source of tumor-derived cell-free DNA (cfDNA) ideally suited for detecting minimal residual disease (MRD). In addition, LBs provide a sensitive means of studying tumor evolution at high temporal resolution. Success rates of LB analyses in neuro-oncology have varied drastically between studies, warranting the deployment of more robust and reproducible assays. Methods: We applied a novel cfDNA methylation-based workflow to a large cohort of cerebrospinal fluid (CSF) samples collected from pediatric brain tumor patients (n>200 patients). Enzymatic methylation sequencing (EM-seq) was adapted for CSF-derived cfDNA inputs in the picogram range, enabling the acquisition of genome-wide cfDNA methylation profiles across the cohort. Utilizing non-oncological cfDNA profiles and CNS tumor DNA methylation datasets as a reference, we developed an innovative computational pipeline that incorporates DNA methylation imputation and deep learning of a neural network. In addition, deconvolution of cfDNA profiles facilitated classification of low tumor burden samples, including those with balanced genomes that would have been missed using previous generation assays. Results: Our CSF-based classifier, M-PACT (Methylation-based Predictive Algorithm for CNS Tumors), yielded accurate tumor detection and entity prediction (AUC=0.9) in our benchmarking cohort (n>100 CSF samples). Proof-of-concept studies showed the potential of this methodology to track tumor evolution in serial CSF samples at both the genetic and epigenetic level, illuminating potential mechanisms driving treatment resistance and recurrence. Conclusions: Collectively, this study provides the framework for robust methylation- based tumor detection and classification of CSF LBs. M-PACT can be applied to aid in tumor diagnostics and to detect MRD during follow-up, warranting prospective validation of its broad applicability and clinical utility in future trials. Citation Format: Tom T. Fischer, Kyle S. Smith, Katie Han, Anna Kostecka, Hong Lin, Daniel Senfter, Tatjana Wedig, Nathalie Schwarz, Natalia Stepien, Sibylle Madlener, Christine Haberler, Esther Hulleman, Sandeep K. Dhanda, Stefan M. Pfister, Santhosh Upadhyaya, Amar Gajjar, Giles W. Robinson, Joonas Haapasalo, Hannu Haapasalo, Kristiina Nordfors, Johannes Gojo, Kendra K. Maass, Kristian W. Pajtler, Paul A. Northcott. M-PACT: Methylation-based predictive algorithm for CNS tumor liquid biopsies [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B012.

Abstract PR014: Robust disease monitoring using CSF liquid biopsies collected from children undergoing cellular therapy for malignant central nervous system tumors

Abstract Background: Central nervous system (CNS) tumors remain the leading cause of cancer-related mortality in children, necessitating more effective treatment options. Chimeric Antigen Receptor T-cells (CAR-T) have emerged as a promising strategy to treat CNS tumors, with B7H3 (CD276) representing an attractive target due to its high expression across a broad range of entities. B7H3-CAR-T therapy is currently being evaluated in a St. Jude Children’s Research Hospital Phase I clinical trial (NCT05835687) for the treatment of relapse/refractory pediatric CNS tumors. Monitoring disease progression after CAR-T infusion by magnetic resonance imaging (MRI) remains challenging, emphasizing the need for more sensitive biomarkers of treatment response. Detection of circulating tumor DNA (ctDNA) in cerebrospinal fluid (CSF) liquid biopsies holds tremendous potential for minimal residual disease (MRD) monitoring in the clinical setting. Here, we leverage CSF liquid biopsies for longitudinal disease profiling in pediatric CNS tumor patients receiving B7H3-CAR-T immunotherapy. Methods: CSF samples were collected from Ommaya reservoirs of 9 pediatric patients with relapse/refractory CNS tumors undergoing B7H3-CAR-T therapy. CSF was sampled at study enrollment, and weekly intervals pre- and post-infusion. Cell-free DNA (cfDNA) was extracted from 115 longitudinally collected CSF samples and subjected to enzymatic methylation sequencing (EM-seq). Implementation of a custom computational workflow enabled detection of tumor-derived copy number variations (CNVs), estimation of malignant vs. non-malignant fractions, and molecular classification of tumor entity. Results: Tumor-derived CNVs were detected in 7/9 (78%) CSF samples collected at enrollment, prior to immunotherapy. Liquid biopsy-inferred CNV profiles and entity classifications were highly concordant with matched tumor tissue profiles. Chromosomal alterations that were restricted to CSF profiles indicated clonal evolution. Increased ctDNA burden was repeatedly observed after B7H3-CAR-T infusions, suggesting subclinical antitumor activity. Transient subclonal alterations emerging in response to treatment were also identified in a subset of patients. Conclusions: EM-seq is a feasible method for serial tracking of ctDNA burden in patients receiving cellular immunotherapy. CSF liquid biopsies capture the global landscape of tumor heterogeneity and genetic alterations that arise during therapy, providing a sensitive platform for detecting clinical response and disclosing potential mechanisms of treatment resistance. Citation Format: Anna Kostecka, Kyle S Smith, Katie Han, Hong Lin, Deanna Langfitt, Tara Walhart, Stephen Gottschalk, Giedre Krenciute, Christopher DeRenzo, Kelsey Bertrand, Paul A Northcott. Robust disease monitoring using CSF liquid biopsies collected from children undergoing cellular therapy for malignant central nervous system tumors [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr PR014.

Tumor-Promoted Changes in Pediatric Brain Histology Can Be Distinguished from Normal Parenchyma by Desorption Electrospray Ionization Mass Spectrometry Imaging

Background: Central nervous system (CNS) tumors are the second most frequent type of neoplasm in childhood and adolescence, after leukemia. Despite the incorporation of molecular classification and improvement of protocols combining chemotherapy, surgery, and radiotherapy, CNS tumors are still the most lethal neoplasm in this age group. Mass spectrometry imaging (MSI) is a powerful tool to map the distribution of molecular species in tissue sections. Among MSI techniques, desorption electrospray ionization (DESI-MSI) has been demonstrated to enable reliable agreement with the pathological evaluation of different adult cancer types, along with an acceptable time scale for intraoperative use. Methods: In the present work, we aimed to investigate the chemical profile obtained by DESI-MSI as an intraoperative surgical management tool by profiling 162 pediatric brain biopsies and reporting the results according to the histopathology and molecular profile of the tumors. Results: The 2D chemical images obtained by DESI-MSI allowed us to distinguish tumor-transformed tissue from non-tumor tissue with an accuracy of 96.8% in the training set and 94.3% in the validation set after statistical modeling of our data using Lasso. In addition, high-grade and low-grade tumors also displayed a distinct chemical profile when analyzed by DESI-MSI. We also provided evidence that the chemical profile of brain tumors obtained by DESI-MSI correlates with methylation-based molecular classes and specific immunophenotypes found in brain biopsies. Conclusions: The results presented herein support the incorporation of DESI-MSI analysis as an intraoperative assistive tool in prospective clinical trials for pediatric brain tumors management in the near future.

Abstract B071: Identifying the clinical utility of CSF as a source of liquid biopsy in pediatric brain tumors

Abstract Pediatric tumors of the central nervous system (CNS) are a leading cause of cancer-related childhood mortality. Along with imaging, it is essential to molecularly characterize tumor tissue for the diagnosis, treatment, and prognosis of these cancers. Biopsies of deeply-seeded lesions may not be possible or may carry significant risks. On the other hand, liquid biopsy, using cerebral spinal fluid (CSF), provides a minimally invasive alternative to identify and monitor tumor DNA at crucial time points, from diagnosis to follow-up. This allows for molecular diagnosis, identification of therapeutic targets, monitoring response to therapy, and early detection of recurrence or progression. The aim of our study was to assess the practicality and usefulness of liquid biopsies in a diverse group of CNS tumor patients. We used a combination of methods, including a targeted hybridization capture panel and low-pass whole genome sequencing (LP-WGS) based on the sample characteristics. We analyzed a total of 243 CSF samples from patients with CNS tumors including: low-grade glioma (LGG; N=57), high-grade glioma (HGG; N=53), medulloblastoma (MB; N=40), germinoma (CNS-GCT; N=29), and no prior biopsy (N=42). We found somatic mutations in 88% of CSF samples from HGG and 67% from LGG with known tumor DNA variants and sufficient sequencing quality. It's important to note that in LGG patients, samples collected from lumbar puncture were positive only in disseminated cases, while a higher positivity rate was found in cases where CSF was collected from ventricular spaces. Moreover, we observed positive copy number alterations (CNA) in CSF samples collected from HGG, embryonal tumors, and CNS-GCT patients at the time of diagnosis and follow-up with a sensitivity of 64%. Within our sample cohort that had an unknown or query tumor due to no prior biopsy, we were able to detect diagnostic, targetable mutations and/or a positive CNA profile in 30% of cases. This supports the utility of liquid biopsy as a diagnostic tool in in CNS lesions. This tool may also assist in monitoring for relapse in high-grade tumors. For example, in a case study, we were able to detect recurrent MB by indication of a positive CNA profile in keeping with the primary tumor CNV, six years post-surgical resection. In CNS- GCT patients, we found that LP-WGS was highly sensitive at diagnosis as we have observed similar CNV in both CSF and tumor DNA. In summary, the utility of our liquid biopsy platform in the context of CNS cancers is an impactful tool that can aid clinicians in diagnosis, treatment and monitoring disease in a minimally invasive manner. Citation Format: Liana Nobre, Mansuba Rana, Yoshiko Nakano, Ian Burns, Robert Siddaway, Richard Yuditskiy, Cyril Li, Andrew Bondoc, Anthony Liu, Uri Taboori, Cynthia Hawkins. Identifying the clinical utility of CSF as a source of liquid biopsy in pediatric brain tumors [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B071.

Brachyury Expression in Atypical Teratoid/Rhabdoid Tumor.

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare, highly aggressive central nervous system tumor of childhood with variable morphologic features, which is characterized by alterations in SWI/SNF complex, such as SMARCB1/INI1 or SMARCA4/BRG1 loss. Poorly differentiated chordoma is the differential diagnosis, particularly in the infratentorial region of older children and the use of brachyury in such conditions is under debate. We investigated the brachyury expression in 44 samples of AT/RT from 40 patients. All AT/RTs except 2 infratentorial tumors were negative for brachyury (2 clones: A-4 and EPR18113). Both brachyury-positive tumors (one diffuse and one patchy expression) involved the clivus of children younger than 2 years old. The DNA methylation profile of one of these tumors showed epigenetic similarity to reference examples of chordoma in 2 public unsupervised and one supervised analysis systems. The second tumor exhibited a classical epigenetic microarray pattern found in samples with degraded DNA. We revised 2 initial AT/RT diagnoses as poorly differentiated chordoma based on the morphology, brachyury expression, topographical features, and methylation profile. Differentiating poorly differentiated chordoma from AT/RT could be challenging; brachyury expression can be useful in diagnosing poorly differentiated chordoma over AT/RT in suitable clinical and radiological settings.

Differential Replication and Oncolytic Effects of Zika Virus in Aggressive CNS Tumor Cells: Insights from Organoid and Tumoroid Models

Central nervous system (CNS) cancers are responsible for high rates of morbidity and mortality worldwide. Malignant CNS tumors such as adult Glioblastoma (GBM) and pediatric embryonal CNS tumors such as medulloblastoma (MED) and atypical teratoid rhabdoid tumors (ATRT) present relevant therapeutic challenges due to the lack of response to classic treatment regimens with radio and chemotherapy. Recent findings on the Zika virus’ (ZIKV) ability to infect and kill CNS neoplastic cells draw attention to the virus’ oncolytic potential. Studies demonstrating the safety of using ZIKV for treating malignant CNS tumors, enabling the translation of this approach to clinical trials, are scarce in the literature. Here we developed a co-culture model of mature human cerebral organoids assembled with GBM, MED or ATRT tumor cells and used these assembloids to test ZIKV oncolytic effect, replication potential and preferential targeting between normal and cancer cells. Our hybrid co-culture models allowed the tracking of tumor cell growth and invasion in cerebral organoids. ZIKV replication and ensuing accumulation in the culture medium was higher in organoids co-cultured with tumor cells than in isolated control organoids without tumor cells. ZIKV infection led to a significant reduction in tumor cell proportion in organoids with GBM and MED cells, but not with ATRT. Tumoroids (3D cultures of tumor cells alone) were efficiently infected by ZIKV. Interestingly, ZIKV rapidly replicated in GBM, MED, and ATRT tumoroids reaching significantly higher viral RNA accumulation levels than co-cultures. Moreover, ZIKV infection reduced viable cells number in MED and ATRT tumoroids but not in GBM tumoroids. Altogether, our findings indicate that ZIKV has greater replication rates in aggressive CNS tumor cells than in normal human cells comprising cerebral organoids. However, such higher ZIKV replication in tumor cells does not necessarily parallels oncolytic effects, suggesting cellular intrinsic and extrinsic factors mediating tumor cell death by ZIKV.

Unconventional Histopathological Features With KIAA1549::BRAF Fusion in Advanced Prostatic Adenocarcinoma.

This report delineates an intriguing example of advanced prostatic adenocarcinoma displaying distinctive histopathological characteristics associated with a KIAA1549::BRAF fusion, a genomic anomaly predominantly identified in central nervous system tumors. A 66-year-old man, presenting with acute renal failure, exhibited metastatic disease involving pelvic soft tissue, bladder, liver, and bone. Histological examination revealed a markedly unconventional morphology within the prostate, characterized by infiltrative tumor sheets exhibiting abundant vacuolated cytoplasm, hyperchromatic nuclei, and irregular nuclear membranes, distinct from typical prostatic adenocarcinoma. Immunophenotyping confirmed NKX3.1 positivity and GATA3 negativity. Molecular analysis revealed the rare KIAA1549::BRAF fusion alongside pertinent mutations in phosphatidylinositol 3-kinase, phosphatase and tensin homolog, and tumor protein 53 genes. Despite diverse therapeutic interventions targeting mitogen-activated protein kinase signaling and subsequent clinical trial enrollment, disease progression remained relentless, culminating in the patient's demise within 4 years of diagnosis. This report highlights the exceptional histopathological presentation associated with KIAA1549::BRAF fusion in prostatic adenocarcinoma, emphasizing the need for a deeper comprehension of its implications on disease behavior and therapeutic responsiveness in similar instances.

Socioeconomic Factors Associated With Participation in Postmortem Tissue Donation in Pediatric Central Nervous System Tumors.

The gift of postmortem tissue donation is critical to pediatric central nervous system (CNS) research. As a "Center of Excellence" for the Gift from a Child Program, our institution has a well-established postmortem tissue donation program. Our objective was to determine if differences exist between patients who participated in and those that declined research-based autopsy. We performed a single-institution retrospective chart review of pediatric patients with CNS malignancies who died from their disease between January 1, 2021 and December 31, 2022. Individual clinical, demographic, and socioeconomic data were assessed. Population-level data were estimated using Zip Code Tabulation Areas. Descriptive statistics were used to compare categorical data. Among the 23 patient families approached during the study time frame, 8/23 (35%) consented to participation. In the consented (C) versus declined (D) group, there was a higher percentage of White, non-Hispanic/Latino patients by self-reported race (C: 88% vs. D: 55%), and no patients who identified as Asian or Hispanic/Latino (C: 0% and 0% vs. D: 13% and 27%). Of all patients approached, two required interpreters (9%), and both families declined participation. The rate of private insurance was higher in the consented group (C: 75% vs. D: 47%) compared to Medicaid as primary insurance in the declined group (C: 13% vs. D: 53%). CONCLUSIONS: Future research should aim to understand and improve identified disparities to ensure research advancements benefit all children with CNS malignancies. One area we plan to address is improved communication with non-English-speaking families by partnering with our interpreter services.

CTIM-02. PIONEERING QUAD-TARGETING CAR T CELL THERAPY IN PEDIATRIC CNS TUMORS – ANALYSIS FROM THE INITIAL PATIENTS TREATED ON THE FIRST-IN-HUMAN PHASE 1 TRIAL BRAINCHILD-04

Abstract BACKGROUND BrainChild-04 is a first-in-human clinical trial of quad-chimeric antigen receptor (CAR) T cell therapy for children and young adults with central nervous system (CNS) tumors. This trial administers repeated locoregional CAR T cells targeting B7-H3, EGFR, HER2, and IL-13Ralpha2 (“quad-CAR T cells”), leveraging multi-antigen targeting to address the tumor heterogeneity of high-grade CNS tumors. METHODS The primary endpoints are feasibility and safety, and secondary endpoints are disease response and correlative studies of CAR T cell activity. The trial utilized a Bayesian Optimal Interval (BOIN) statistical design with three planned dose regimens(DR). There are 2 arms with weekly delivery for 3 weeks of a 4-week cycle:(A) –diffuse intrinsic pontine glioma (DIPG), (B) –non-pontine diffuse midline glioma (DMG) or other relapsed CNS tumors. RESULTS Enrolled patients include DMG N=6, DIPG N=5, other CNS tumors N=4. Of the 15 enrolled patients, 7 have been infused with 8 awaiting infusions. A total of 33 intracranial CAR T doses have been delivered, including Arm A DR 1 (N=1), Arm B DR 1 (N=3), DR2 (N=3). The most common adverse events have been grade 1-2 fever (7/7 patients), grade 1-3 headache (6/7), and grade 1-2 nausea/vomiting (6/7). There have been no DLTs and no cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity (ICANS). CTCAE and tumor inflammation-associated neurotoxicity are both being captured. All treated patients are alive with median follow up time post-initial infusion of 93(14-198) days. CAR T cells were detected by flow cytometric analysis of CSF post-infusion in 14/24 CSF samples. Radiographic response, CSF circulating tumor DNA, targeted mass spectrometry, and cytokine analysis will be presented. CONCLUSIONS Our preliminary experience suggests tolerability of locoregional delivery of quad-CAR T cells at doses currently evaluated. The trial remains ongoing and these data support continued evaluation of this product to better assess anti-tumor activity in patients with CNS tumors, including DIPG/DMG.

BIOM-55. SENSITIVITY OF IMMUNOHISTOCHEMISTRY WITH BRAF VE1 ANTIBODY FOR BRAF V600E IN PRIMARY CENTRAL NERVOUS SYSTEM TUMORS

Abstract BACKGROUND BRAF gene encodes for a key protein of the RAS-RAF-MEK-ERK pathway. BRAF alterations are found in a variety of primary central nervous system (CNS) tumors ranging from 3% of glioblastomas to 60% of pleomorphic xanthoastrocytomas. BRAF V600E mutation is the most common BRAF alteration found in CNS malignancies, and it has been successfully targeted with BRAF/MEK inhibitors. Novel BRAF inhibitors, still in development, have shown promising antitumor activity. Next-generation sequencing (NGS) has become a standard test in the era of histo-molecular diagnosis, but it can be unavailable or inaccessible, and results usually take longer. Immunohistochemistry (ICH) with VE1 antibody for BRAF V600E protein has shown high discordant results with sequencing in other tumor types. We aimed to establish the concordance of BRAF VE1 and NGS sequencing in CNS tumors. METHODS Single-center retrospective analysis of patients with BRAF V600E mutant CNS tumors by NGS testing. RESULTS 30 patients with BRAF V600E mutant primary CNS tumors by NGS were included, 18 were male. 15 were classified as IDH-wildtype gliomas, 4 low grade neuroepithelial gliomas, 8 pleomorphic xanthoastrocytoma, 2 pilocytic astrocytomas and 1 papillary craniopharyngioma. IHC testing with BRAF VE1 antibody was done at the initial pathological classification in 23 of the cases being positive in 15 and negative in 8 cases. In 7 cases IHC was not done but has been requested for retrospective analysis and results are pending. Sensitivity for BRAF VE1 IHC was 65%. CONCLUSION When compared to NGS testing, ICH with BRAF VE1 antibody for BRAF V600E in CNS tumors shows modest sensitivity, being a limited tool when results are needed promptly or NGS is inaccessible. Determining specificity of the test will be crucial to establish its reliability for patient selection. Sequencing should be obtained when possible and remains the more reliable method for detecting V600E.

DISP-13. TELEHEALTH UTILIZATION IN NEURO-ONCOLOGY: EXPERIENCE AFTER THE COVID-19 PANDEMIC

Abstract BACKGROUND Central nervous system (CNS) tumors are frequently characterized by physical disabilities, and treatment is often associated with side effects, as well as financial toxicity and loss of income owing to disease-related neurological deficits. Treatment at centers with specialized neuro-oncology care is associated with an overall survival benefit. However, access to such centers can be limited for many patients. Telehealth services represent an option for improving access to specialized care. During the COVID-19 pandemic public health emergency (PHE), regulatory and reimbursement changes provided patients improved access to neuro-oncology by telehealth. METHODS We retrospectively analyzed our institutional utilization of telehealth visits in the neuro-oncology vs solid tumor oncology practice after the COVID-19 pandemic. RESULTS Between July 2020 and April 2021, telehealth represented 24.1% of all neuro-oncology visits compared to 13.3% for all solid tumor groups. Between May 2021 and April 2023, telehealth visits remained frequent in neuro-oncology compared to solid tumor groups (34.6% vs 15.2%). Utilization rates declined across the practice in the year following expiration of the COVID-19 PHE in May 2023, though remained high for neuro-oncology at 34.1% vs 15.2% for solid tumor groups. Overall, telehealth visit utilization for neuro-oncology has remained more than double that of the oncology practice as a whole. CONCLUSIONS The striking difference between telehealth visit utilization in neuro-oncology compared with general medical oncology indicates that patients with CNS tumors, and those that provide care for these patients, have come to depend on this mode of care delivery. Even after expiration of the COVID-19 PHE, telehealth use remains high in neuro-oncology at our institution. Prospective evaluation to determine the safety of and clinical outcomes associated with telehealth visits for individuals with CNS tumors are critically needed. Such data may promote regulatory and reimbursement reform enabling broader adoption, service sustainability, and improved access to specialized care.

CNSC-58. BIOPROCESSING OF VIABLE SURGICAL PEDIATRIC BRAIN TUMOR SPECIMENS FOR GENOME-GUIDED PERSONALIZED DRUG TESTING

Abstract Novel treatment approaches are urgently needed for pediatric central nervous system (CNS) tumors as they are the leading cause of cancer-related deaths in children. A lack of research materials impedes progress towards developing such therapies. Although various brain cancer biobanks exist, these rarely store viable patient-derived tissue and cells for live cell analyses, including cell fate assays and testing for drug sensitivities. We propose that a biorepository of viable cell dissociates and tissue broadly representing CNS tumor entities overcomes these limitations. From a combination of molecular diagnoses and histopathologic assessment of over 120 samples collected, we generated a biorepository of roughly 35 distinct entities of pediatric CNS tumors in our Stanford neuro-bioprocessing cohort. Based on the Central Brain Tumor Registry of the United States, the proportion of subtypes represented in our cohort match that of the general population with exceptions. We established a standardized bioprocessing pipeline that can be used as a template for tissue collection and model development in the broader disease context and for multiple downstream applications. Our emphasis on cryostorage of viable cells and tissue facilitates ad hoc live cell analyses. In addition to gaining a better understanding of tumor pathophysiology, we attempted a rapid bed-to-bench-to-bedside approach using comparative RNA expression profile analyses in an individual patient’s pilocytic astrocytoma. Novel drug targets were identified by analyzing RNA transcripts that are highly expressed (outliers) compared with a compendium of 12,747 brain and non-brain tumor samples. We validated outliers as drug targets using acute cell isolates, and identified a novel target in recurrent low-grade glioma. These studies illustrate that biobanking of viable patient-derived material enables developing personalized therapies with the goal of improving patient outcomes. As demonstrated here, patient-derived acute cell isolates facilitate identifying drug vulnerability, creating an opportunity for more personalized treatment of patients with CNS tumors.

Evaluation of ploidy and the DNA index by flow cytometry in central nervous system tumors: a review.

Research on central nervous system tumors (CNSTs) has a significant impact on the diagnosis and prognosis of patients. Currently, CNSTs are classified according to the schema proposed by the World Health Organization (WHO), which considers clinical, histopathological, and molecular characteristics, highlighting the importance of tumor biology for accurate diagnosis and optimal treatment approaches. Despite these advances, assessing DNA ploidy-a marker of tumor aggressiveness-remains complex in CNSTs. This review investigates the utility of DNA index (DNAi) and DNA ploidy analysis by flow cytometry in diagnosing CNSTs and prognosing their outcomes. We systematically reviewed studies in the PubMed database from 1990 to the present using the keywords "DNA Index", "Brain", "Flow cytometry", and "Ploidy". We identified 151 studies, 36 of which met our inclusion criteria. We found considerable variation in sample sizes and methodological variation across the studies. Discrepancies between the reported DNAi and ploidy values were observed. Aneuploidy is generally associated with more aggressive tumors, although exceptions exist. Higher DNAi levels correlate with increased malignancy, notably in glioblastomas, astrocytomas, and meningiomas, whereas diploid astrocytomas and oligodendrogliomas are associated with shorter survival rates. DNA ploidy assessment via flow cytometry could predict CNST behavior, yet methodological issues with tissue selection, adequate control samples, and technique variability remain. DNAi and ploidy assessments show promise as prognostic markers in CNSTs. However, the standardization of flow cytometry protocols and alignment with the current WHO classification schema are essential steps to integrate ploidy analysis in routine CNST assessment.

EPID-10. THE INCIDENCE OF PRIMARY BRAIN TUMORS IN JAPAN IN 2016-2019

Abstract The national cancer registries in Japan have started since 2016 and the actual number of cancer patients in including primary central nervous system (CNS) tumors in Japan was revealed. Average number of primary CNS tumors in 2016-2019 was 29,492 and the crude incidence rate per 100,000 people (CIR) was 23.30. Malignant and benign CNS tumors was 6,696 (22.7%) and 22,796 (77.3%) and each CIR was 5.29 and 18.00, respectively. Among 29,492 tumors, 10,537 (35.7%) meningioma, 5,217 (17.7%) pituitary adenoma, 4,537 (15.4%) neuroepithelial tumor, 2,730 (9.3%) neurinoma and 1,166 (4.0%) primary CNS lymphoma (PCNSL) were reported. Regarding to malignant brain tumors, 2,071 glioblastoma, 362 astrocytoma grade II, 390 anaplastic astrocytoma grade III, 138 pilocytic astrocytoma,182 oligodendroglioma grade II, 154 anaplastic oligodendroglioma grade III, 140 ependymal tumors, 128 embryonal tumors including 91 medulloblastoma, 211 germ cell tumor (GCT) were found. CIR of neuroepithelial tumor, glioblastoma, PCNSL, embryonal tumors and GCT were 3.64, 1.68, 0.93, 0.10 and 0.17, respectively. According to the Central Brain Tumor Registry of the United States (CBTRUS) (2016-2020), CIR in the US was 26.73, and age-adjusted incidence rates of primary CNS tumors per 100,000 population in the US based on the US population in 2000 (AIR) was 24.83 and AIR in Japan was 17.15. AIR of glioblastoma in the US and Japan was 3.27 and 1.05, AIR of PCNSL was 0.44 and 0.51, AIR of embryonal tumors was 0.21 and 0.16, AIR of GCTs was 0.08 and 0.27, and AIR of meningioma was 9.73 and 5.11, respectively. This report demonstrated that the incidence of neuroepithelial tumors and embryonal tumors in Japan was approximately half to one-third, whereas that of GCTs in Japan was approximately 3 times comparing to the US.

EPCO-32. PROSPECTIVE GERMLINE SEQUENCING OF PATIENTS WITH GLIOMAS, GLIONEURONAL OR NEURONAL TUMORS

Abstract BACKGROUND Several genetic syndromes have been linked to the development of central nervous system (CNS) tumors; however, the prevalence and clinical significance of germline pathogenic variants in this population remain unclear. METHODS 2,367 patients with a glioma, glioneuronal, or neuronal tumor (WHO grade 1-4) ages 0.2-93.8 years underwent tumor and matched normal sequencing with MSK-IMPACT. Germline variants and copy-number variants affecting 90 well-established cancer predisposing genes were analyzed; the presence of biallelic inactivation was determined using FACETS. RESULTS Eleven percent harbored germline pathogenic mutations in high-, moderate-, and low-penetrance genes. High- and moderate-penetrance genes included CHEK2 (n=32, 1.3%), BRCA2 (n=10; 0.4%), TP53 (n=9; 0.4%), NF1 (n=6; 0.2%), and mismatch repair (MMR) genes (n=20, 0.9%). Low-penetrance genes included monoallelic MUTYH (n=42; 1.8%) and the APC I1307K variant (n=28, 1.2%). Biallelic inactivation was found in all tumors from patients with germline TP53 and NF1 mutations, with lower rates in tumors from patients with a germline MMR alteration (53%). Biallelic inactivation was rare among patients with a germline mutation in homologous recombination pathway (HRD) genes (27%), and in the aforementioned low-penetrance APC (15.3%) and MUTYH (10.2%) variants. All patients with biallelic inactivation of an MMR gene were hypermutated. Biallelic inactivation of MMR genes and TP53 were observed in IDH-mutant astrocytoma and IDH-WT gliomas, while biallelic inactivation of NF1 and somatic IDH1/2 mutation were mutually exclusive. When examining the age at diagnosis among patients with germline alterations, tumors with biallelic inactivation were diagnosed at a younger age compared to tumors with monoallelic alterations (37.7 vs 51.6 years, p=0.002). CONCLUSION Clinical germline sequencing identifies a germline mutation in a high proportion of patients with CNS tumors. Biallelic inactivation was most commonly identified in tumors from patients with germline TP53 or NF1 mutations and were less common in patients with a germline MMR alteration.

PATH-43. MALIGNANT TRANSFORMATION OF MENINGEAL MELANOCYTOMA - GENETIC ALTERATIONS AND RESPONSE TO CHECKPOINT BLOCKADE IMMUNOTHERAPY

Abstract INTRODUCTION Meningeal melanocytomas are uncommon tumors that develop from leptomeningeal melanocytes. These tumors can exhibit aggressive behavior, leading to symptoms due to compression and potential invasion of nearby central nervous tissue. Case: In this report, we discuss the case of a 45-year-old man who was diagnosed 18 years ago with a meningeal melanocytoma in the right temporal region. He underwent complete resection with each recurrence and received focal intensity-modulated radiation therapy after a third recurrence in 2013. In May 2022, he developed progressive headaches and diplopia secondary to tumor recurrence on the right temporal region. Resection revealed that the tumor had progressed to malignant meningeal melanoma with 34 mitoses per 10 high-power fields. Next-generation sequencing (NGS) showed GNAQ mutation confirming tumor of central nervous system (CNS) origin, and also showed an SF3B1 mutation, indicating aggressive behavior. Several chromosomal abnormalities were also detected. Systemic workup revealed liver, lung, and bone metastasis. Liver biopsy confirmed meningeal melanoma of central origin. The patient received radiosurgery with a total of 30Gy over five fractions to intracranial surgical cavity, followed by three cycles of nivolumab and relatlimab. Unfortunately, the patient experienced severe intracranial and systemic progression, leading to his death six months after the malignant transformation. DISCUSSION Meningeal melanocytomas are rare however these tumors have a high recurrence rate with potential malignant transformation over time. NGS is a valuable tool for confirming the CNS origin of the tumor and predicting its aggressive behavior. Despite microscopic similarity with cutaneous melanomas, meningeal melanocytomas have different pathogenesis and do not seem to respond to immunotherapy, as observed in this case.

PATH-46. DETECTION OF CDKN2A/B HOMOZYGOUS DELETION BY DNA METHYLATION AND DNA NEXT GENERATION SEQUENCING: A COMPARISON

Abstract CDKN2A/B homozygous deletion status is critical for grading of several central nervous system (CNS) tumors, including IDH mutant astrocytoma, pleomorphic xanthoastrocytoma, and meningioma. CDKN2A/B status can be assed using variety of methods, but the accuracy varies due to technical and analytical variables. Here we sought to compare sensitivity of CDKN2A/B homozygous deletion detection by NGS and DNA methylation array derived copy number analysis. We retrospectively analyzed 100 CNS tumors diagnosed at NYU Langone Health between 2020 and 2023. All tumors were profiled by whole genome DNA methylation profiling using the Illumina EPIC array. Copy numbers were analyzed using the ‘conumee’ R package and visual inspection. Next-generation sequencing (NGS) analysis was performed by NYU Langone Genome PACT, a 510(k) FDA cleared (K202304) matched tumor-normal 607 gene panel. Variant allele frequency of canonical driver mutations was used to molecularly estimate tumor cell content. Discrepant cases were assed using targeted qPCR. Our cohort of 100 CNS tumors included glioblastoma (N=75), IDH mutant astrocytoma (N=14), oligodendroglioma (N=4), pleomorphic xanthoastrocytoma (N=2), meningioma (N=1), infantile hemispheric glioma (N=1), central neurocytoma (N=1), diffuse midline glioma K27-altered (N=1), and anaplastic pilocytic astrocytoma (N=1). By DNA methylation, CDKN2A/B homozygous deletion was detected in 54 cases, hemizygous deletion was detected in 13 cases, and no deletion was detected in 33 cases. By NGS, CDKN2A/B homozygous deletion was detected in 31 cases, hemizygous deletion was detected in 28, and no deletion was detected in 41 cases. DNA methylation detected a homozygous deletion in 23 cases that were not detected by NGS. All cases of homozygous deletion detected by NGS were also detected by DNA methylation. DNA methylation derived copy number assessment is more sensitive for CDKN2A/B homozygous deletion than next generation sequencing.