IDH-wildtype Gliomas Research Articles

Homozygous CDKN2A/B deletions in low- and high-grade glioma: a meta-analysis of individual patient data and predictive values of p16 immunohistochemistry testing.

CDKN2A/B deletions are prognostically relevant in low- and high-grade gliomas. Data on this is derived from heterogeneous series, an accurate estimation of survival risk from homozygous CDKN2A/B deletion is missing. Besides genetic testing, p16-immunohistochemistry (IHC) as a less cost intensive means for indirect detection of CDKN2A/B alterations is possible but not validated in larger datasets. The present meta-analysis aimed to (1) reconstruct individual patient data (IPD) and estimate overall survival (OS) stratified by CDKN2A/B status from all literature and to (2) determine accuracy of p16 testing for CDKNA2/B detection from published studies. For survival analysis according to CDKN2A/B status 460 records were screened, four articles with 714 participants were included. In IDH-wildtype (IDH-wt) gliomas, 57.07% harbored the deletion compared to 9.76% in IDH-mutant (IDH-mut) gliomas. Median OS of patients with IDH-wt gliomas and homozygous CDKN2A/B deletion was 13.0 months compared to 18.0 months with non-deleted CDKN2A/B (p = 0.014, Log-Rank). With homozygous deletion of CDKN2A/B the risk of death was increased by 1.5 (95%-CI 1.1-2.1). Median OS in patients with IDH-mut gliomas without CDKN2A/B deletion was 92.0 months compared to 40.0 months with CDKN2A/B deletion (p < 0.001, Log-Rank). CDKN2A/B deletions were associated with a significantly shorter OS (HR = 3.2; 95%-CI 2.2-5.5). For p16 IHC analysis, 10 eligible studies with 1087 examined samples were included. The cut-off for retention differed between the studies. In 588/662 p16 retained cases CDKN2A/B deletions was not detected, implying a negative predictive value (NPV) of p16 staining of 88.8%. Conversely, 279/425 p16 absent cases showed a CDKN2A/B deletion resulting in a positive predictive value (PPV) of 65.6%. Sensitivity of p16 staining for CDKN2A/B detection was 79.0%, specificity 80.1%. Highest diagnostic accuracy of p16 IHC was reached with a cut-off of > 5% and within IDH-mut glioma.

PATH-52. DIFFERENCES IN GENE EXPRESSION, GENOME-WIDE METHYLATION AND METABOLITES IN ADULT DIFFUSE GLIOMAS

Abstract Metabolic reprogramming is a hallmark of cancer, including diffuse gliomas. IDH1 and IDH2 are key enzymes linking cellular metabolism to epigenetic regulation and redox states. IDH1/IDH2 enzymes catalyze the conversion of isocitrate to α-ketoglutarate, while the mutant enzymes increase the production of D-2-hydroxyglutarate, an oncometabolite that induces epigenetic changes, leading to gene expression alterations. Understanding how epigenetic alterations affect metabolic gene expression and metabolite levels in diffuse gliomas could help identify diagnostic biomarkers and therapeutic targets. We studied the expression of metabolism-related genes, metabolites, and genome-wide methylation status, which will facilitate an integral understanding of the metabolic changes in IDH-mutant and IDH-wildtype gliomas. Study design included 47 fresh frozen tissue samples. RNA was extracted and used for gene expression analysis using the NanoString platform (nCounter® Metabolic Pathways Panel), while extracted DNA was used for targeted sequencing with a panel interrogating 600 genes and for genome-wide methylation analysis using the Illumina Epic v2. In addition, unbiased metabolomic analysis by mass spectrometry was performed in 25 tissue and CSF samples out of 47 samples. Methylation status, gene expression and metabolite levels were compared between IDH-mutant and IDH-wildtype gliomas. Results showed significant differences in DNA methylation, gene expression and metabolites between IDH-mutant and IDH-wildtype gliomas. UPP1, an enzyme involved in uracil metabolism, was studied in depth to understand the interplay between DNA methylation, gene expression, and metabolic reprogramming in diffuse glioma. Epigenetic analysis revealed that the CpG sites within the UPP1 gene displayed reduced methylation in IDH wild-type compared to IDH-mutant tumors. IDH wild-type tumors showed higher UPP1 expression compared to their IDH-mutant counterparts. Consequently, we observed higher levels of uracil in tissue and CSF samples from patients with IDH wild-type gliomas. These data provide a framework to study the relationship between mutations, methylation, gene expression and metabolism in diffuse gliomas.

TMIC-26. IMMUNE CELL DYNAMICS WITHIN GLIOMAS: THE INFLUENCE OF GRADE AND IDH STATUS

Abstract Mutations in isocitrate dehydrogenase (IDH) are known to significantly impact the prognosis and biology of diffuse gliomas. A number of studies have compared the immune microenvironment of IDH-wildtype glioma versus IDH-mutant glioma, and have also characterized the impact of mutant-IDH on lymphocytes. However, few studies have explored how mutant-IDH may affect tumors as they progress and increase in grade, or have delved into the myeloid immune cell compartment. Thus, we sought to understand whether tumor progression affected intratumoral immune cell composition within IDH-mutant glioma, and aimed to compare IDH-mutant versus IDH-wildtype glioma in both humans and mice. Using bulk RNA sequencing, we compared paired samples from patients with IDH-mutant glioma before and after progression, focusing on differentially-expressed immunological genes and relative immune cell proportions. We also compared grade 4 IDH-mutant astrocytoma cases to IDH-wildtype glioblastoma, performing both transcriptomic and cellular analyses. Finally, we engineered murine glioma cells to test the effect of mutant-IDH alone in the tumor microenvironment. We found that multiple immune-related genes distinguish low- and high-grade IDH-mutant glioma, and that high-grade tumors contain greater proportions of suppressive myeloid cells. When comparing IDH-wildtype to IDH-mutant glioma, we found enrichment of suppressive macrophages and myeloid-derived suppressor cells (MDSC) in IDH-wildtype tumors. Finally, our murine model of IDH-wildtype versus IDH-mutant glioma mirrored many of the myeloid cell shifts observed in human tumors. Our data show that progression of IDH-mutant tumors is a significant immunological phenomenon, associated with marked alterations in the tumor immune microenvironment. We also show that IDH-mutant glioma harbors greater inflammatory signatures and fewer suppressive myeloid cells than IDH-wildtype glioma, and that engineering mutant IDH into murine tumors is sufficient to model these differences. These findings improve our understanding of key intratumoral cell populations that may be harnessed by future immunotherapeutic strategies.

NIMG-44. ELEVATED TRANSLOCATOR PROTEIN 18KDA BINDING IN LOW MEAN DIFFUSIVITY CLUSTERS IS A FEATURE OF THE TRANSFORMING GLIOMA AND IDH MUTANT GLIOMA MICROENVIRONMENT

Abstract Around 95% of low-grade gliomas undergo anaplastic de-differentiation into high-grade gliomas, a process only partially understood from in vivo clinical imaging. 11 patients with suspected transforming gliomas underwent a combined magnetic resonance imaging (MRI) and positron emission tomography (PET) protocol, incorporating post-contrast T1-weighted/FLAIR acquisition for tumour delineation and diffusion tensor imaging. The PET radiotracer [11C]-(R)-PK11195 assessed translocator protein 18kDa (TSPO) distribution, whose upregulation is associated with inflammation/glioma progression. [11C]-(R)-PK11195 binding potential (BPND) maps were generated using the simplified reference tissue model, with the grey-matter cerebellar time-activity curve serving as the reference tissue input function. KMeans clustering of mean diffusivity (MD) intensity values defined spatially distinct “habitats” of high/low MD voxels within the glioma microenvironment. BPND values within high/low MD clustering habitats were evaluated, across glioma grades and isocitrate dehydrogenase (IDH) mutational status. Across all grade 2 and 3 gliomas (n= 6), mean TSPO BPND values in low MD habitats (0.0383 ±0.102) were significantly greater than high MD habitats (-0.045 ±0.142) (p= 0.003). In grade 4 gliomas (n= 5), no significant difference was observed in mean BPND values between low (0.514 ±0.176) and high (0.465 ±0.296) MD habitats (p= 0.543). IDH mutant gliomas (n= 7) exhibited significantly higher mean BPND in low MD habitats (0.116 ±0.225), relative to high habitats (0.052 ±0.287) (p= 0.021). IDH wildtype gliomas (n= 4) showed no significant differences between BPND values in low (0.498 ±0.199) and high MD habitats (0.424 ±0.325) (p= 0.467). Our novel findings demonstrate spatial heterogeneity in TSPO expression within 2/3/IDH mutant gliomas, a characteristic absent from grade 4/IDH wildtype varieties. Regions of restricted diffusion with high TSPO signal in grade 2/3/IDH mutant tumours indicate the heterogenous distribution of active TSPO-expressing immune/neoplastic cell populations, contrasting the homogenous distribution in grade 4/IDH wildtype gliomas, highlighting differences between their inflammatory profile and pathological features.

EPID-32. ELEVATED SERUM IGE IS LINKED TO IMPROVED GLIOBLASTOMA SURVIVAL, PARTICULARLY AMONG FEMALES

Abstract Prior epidemiological research shows a correlation between serum immunoglobulin E (IgE) levels and decreased risk of glioma. However, the relationship between IgE and the prognosis of glioma remains poorly understood. This study seeks to investigate how factors such as sex, tumor subtype, and IgE class influence the association of serum IgE levels with both glioma risk and survival outcomes. METHODS- In this investigation, we conducted a case-control study utilizing participants enrolled in the UCSF Adult Glioma Study from 1997 to 2010. We measured serum IgE levels for total, respiratory, and food allergy in adults diagnosed with glioma (n=1,696), and controls (n=1,135) matched based on age, sex, and race/ethnicity. Logistic regression, adjusted for patient demographics, was employed to evaluate the correlation between IgE levels and glioma risk. Multivariable Cox regression, adjusted for patient-specific and tumor-specific factors, was utilized to compare survival outcomes between the elevated and normal IgE groups. RESULTS- Increased levels of total IgE were linked to a decreased risk of both IDH wildtype (OR=0.65, 95% CI: 0.54-0.78) and IDH mutant glioma (OR=0.65, 95% CI: 0.50-0.85). In multivariable Cox regression analysis, heightened respiratory IgE levels were associated with enhanced survival among individuals with IDH wildtype glioma (HR=0.78, 95% CI: 0.67-0.91). Notably, this improved survival was more pronounced in females (HR=0.71, 95% CI: 0.53-0.96) compared to males (HR=0.80, 95% CI: 0.66-0.97), resulting in median survival improvements of 6.2 months (P&amp;lt;.001) and 1.6 months (P=0.003), respectively. CONCLUSION- Increased levels of serum IgE were associated with reduced risk of glioma overall, and improved prognosis for IDH wildtype glioma, which was particularly strong in females. These findings hint at potential sexual dimorphism in the antitumor activity of IgE-mediated immune responses, suggest an important role for IgE assessment in glioblastoma clinical trial design, and provide justification for investigations into IgE-based therapeutics.

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.

TMET-12. TARGETING AMINO ACID METABOLIC VULNERABILITIES IN GLIOMAS

Abstract Isocitrate dehydrogenase (IDH) wild-type gliomas and IDH mutant gliomas are similar in histologic appearance but differ in their genetic and metabolic backgrounds. This study aimed to reveal the difference in metabolites between IDH-wildtype glioma and IDH-mutant glioma, and to find the effective treatment according to the status of IDH in gliomas. Two artificial cell lines made from human astrocyte were used: NHAE6E7hTERTRas (IDH-wildtype) and NHAE6E7hTERTIDHmut (IDH-mutant). Using capillary electrophoresis- and ion chromatography–coupled mass spectrometry, the amount of asparagine was lower in NHAE6E7hTERTRas cells compared with NHAE6E7hTERTIDHmut cells, whereas the amount of glutamine, glutamate and 2-oxoglutarate in NHAE6E7hTERTIDHmut cells was lower than NHAE6E7hTERTRas cells. L-asparaginase, which converts asparagine into aspartate, was more effective in NHAE6E7hTERTRas cells than NHAE6E7hTERTIDHmut cells. L-asparaginase induced autophagy and inhibition of autophagy by 3-MA suppressed L-asparaginase-induced antitumor effect, which meant that the antitumor effect was at least partially due to the L-asparaginase-induced autophagy. Pharmacological or genetical inhibition of GLUD1 which converts glutamate to 2-oxoglutarate, suppressed proliferation of the cells by inducing ROS and apoptosis in NHAE6E7hTERTIDHmut cells. ROS inhibitor, NAC suppressed GLUD1 inhibitor-induced ROS, apoptosis, and cytotoxicity in NHAE6E7hTERTIDHmut cells, revealing that cytotoxicity by GLUD1 inhibitor was at least partially due to the inhibitor-induced ROS. The experiments using mutant IDH1 overexpressed glioma cell line showed similar sensitivity to GLUD1 inhibitor to NHAE6E7hTERTIDHmut, which suggested that the difference of sensitivity to GLUD1 inhibitor was due to the status of mutant IDH. In vivo experiments, L-asparaginase suppressed the growth of xenografted glioma cells without mutant IDH, whereas GLUD1 inhibitor inhibited the proliferation of xenografted glioma cells with overexpressed mutant IDH1. In conclusion, L-asparaginase and Glud1 inhibitor will be new therapeutic option for IDH-wildtype glioma and IDH-mutant glioma, respectively.

NIMG-34. CXCR4-TARGETED PET IMAGING OF CENTRAL NERVOUS SYSTEM LYMPHOMA AND GLIOMA USING [68GA]GA-PENTIXAFOR

Abstract BACKGROUND Initial results suggest that PET imaging of the chemokine receptor CXCR4 is of considerable interest for differential diagnosis and theranostic approaches. Here, we summarized findings of CXCR4 PET imaging in an institutional series of lymphoma of the central nervous system (CNSL) and glioma. METHODS Twenty-three patients with CNSL and 16 patients with glioma (IDH-wildtype, n=9) underwent PET imaging using the CXCR4-directed tracer [68Ga]Ga-Pentixafor. In 18 patients, serial PET imaging was performed (range, 2-14 scans), resulting in a total of 104 PET scans. For evaluation, PET scans were classified as [68Ga]Ga-Pentixafor-positive and -negative visually, and the maximum standardized uptake value (SUVmax) was obtained from [68Ga]Ga-Pentixafor-PET. RESULTS Twenty-four of all 39 patients (62%) had at least one [68Ga]Ga-Pentixafor-positive PET (CNSL, 57%; glioma, 69%). [68Ga]Ga-Pentixafor-positive PET scans were more common in patients with IDH-wildtype gliomas (89%) than in IDH-mutant gliomas (43%). In patients with [68Ga]Ga-Pentixafor-positive PET, the average SUVmax was 6.4±4.0 in CNSL, and 3.4±1.0 in gliomas (P=0.155). Besides visualization of tumors, [68Ga]Ga-Pentixafor uptake was observed in two patients with radionecrosis. In four CNSL patients who had undergone methotrexate/cytarabine-based first-line therapy, serial PET revealed a significant reduction of SUVmax after chemotherapy completion (average decrease of SUVmax from 4.5±3.8 to 0.6±0.7; P=0.044). In three of those four patients, tumor progression has not been reached (range of time after the follow-up PET, 4-55 months); one patient deceased 44 months after the follow-up PET. In contrast, another patient with an increase in SUVmax from 6.9 to 11.0 after first-line treatment died one month after the follow-up PET. DISCUSSION [68Ga]Ga-Pentixafor PET seems to be of value for non-invasively visualizing and quantifying CXCR4 receptor binding. In CNSL, changes in [68Ga]Ga-Pentixafor uptake following therapy may indicate potential for response assessment. CXCR4-targeting radioligand therapies might be more promising in CNSL than in glioma.

EXTH-70. PRECLINICAL TRIALS OF THE ANTIBODY-DRUG CONJUGATE TISOTUMAB VEDOTIN IN ADULT-TYPE DIFFUSE GLIOMAS

Abstract The gene F3, encoding Tissue Factor (TF), is expressed in many cancers and contributes to their malignancy. Our previous work showed that, among adult-type diffuse gliomas, IDH wild-type (IDHwt) glioblastomas (GBM) express more TF than IDH mutant (IDHmut) gliomas (PMID: 27664011, 30266764, 31222125). Tisotumab vedotin (TisVed), an anti-TF antibody conjugated to monomethyl auristatin E, is a therapeutic designed to target cells expressing TF. We therefore sought to determine the therapeutic potential of TisVed in IDHwt vs. IDHmut gliomas. TisVed was more active against cultured IDHwt GBM cells than IDHmut glioma cells (P&amp;lt;0.0001). This activity was increased by 55% with daily washout of the soluble TF secreted by IDHwt GBM cells. TisVed extended the survival of mice intracranially engrafted with IDHwt GBM by 34% (37.5 days vs. 28 days for IgG control, P=0.006), but not mice with IDHmut glioma (30.5 days, P=0.88). TisVed also reduced the growth of IDHwt GBM flank xenografts by 58% (P=0.045). Unconjugated Tis had no antitumor effect intracranially or in the flank. All 12 flank-engrafted mice treated with Tis, and 9/12 mice treated with TisVed, developed large hematomas in and around the flank xenografts, compared to 0/12 IgG-treated mice (P&amp;lt;0.001). Similarly, a semiquantitative analysis showed that intracerebral hemorrhage was more extensive in Tis/TisVed- treated GBM12 mice than in IgG-treated GBM12 mice (P=0.046). These data indicate that TisVed targets high TF-expressing IDHwt GBM, but not low TF-expressing IDHmut glioma, that its activity is predominately through the vedotin conjugate rather than inhibition of TF signaling, and that it may have some effect against TF-expressing IDHwt GBM, but intracerebral hemorrhage may be a concern.

EXTH-45. PRECLINICAL EVALUATION OF THE ANTIBODY-DRUG CONJUGATE TISOTUMAB VEDOTIN IN ADULT-TYPE DIFFUSE GLIOMAS

Abstract The gene F3, encoding Tissue Factor (TF), is expressed in many cancers and contributes to their malignancy. Our previous work showed that, among adult-type diffuse gliomas, IDH wild-type (IDHwt) glioblastomas (GBM) express more TF than IDH mutant (IDHmut) gliomas (PMID: 27664011, 30266764, 31222125). Tisotumab vedotin (TV), an anti-TF antibody conjugated to monomethyl auristatin E, is a therapeutic designed to target cells expressing TF. We therefore sought to determine the therapeutic potential of TV in IDHwt vs. IDHmut gliomas. TV was more active against cultured IDHwt GBM cells than IDHmut glioma cells (P&amp;lt;0.0001). This activity was increased by 55% with daily washout of the soluble TF secreted by IDHwt GBM cells. TV extended the survival of mice intracranially engrafted with IDHwt GBM by 34% (37.5 days vs. 28 days for IgG control, P=0.006), but not mice with IDHmut glioma (30.5 days, P=0.88). TV also reduced the growth of IDHwt GBM flank xenografts by 58% (P=0.045). Unconjugated tisotumab had no antitumor effect intracranially or in the flank. All 12 flank-engrafted mice treated with tisotumab, and 9/12 mice treated with TV, developed large hematomas in and around the flank xenografts, compared to 0/12 IgG-treated mice (P&amp;lt;0.001). Similarly, a semiquantitative analysis showed that intracerebral hemorrhage was more extensive in tisotumab/TV- treated GBM12 mice than in IgG-treated GBM12 mice (P=0.046). These data indicate that TV targets high TF-expressing IDHwt GBM, but not low TF-expressing IDHmut glioma, that its activity is predominately through the vedotin conjugate rather than inhibition of TF signaling, and that it may have some effect against TF-expressing IDHwt GBM, but intracerebral hemorrhage may be a concern.

EPCO-29. PATHOMICS ANALYSIS IDENTIFIES POTENTIAL SUBTYPES OF DIFFUSE GLIOMAS IN H&amp;E-STAINED WHOLE-SLIDE IMAGES

Abstract IDH status is the first criteria of diagnostic definition for diffuse gliomas in the 2021 WHO classification. While sufficient number of molecular tools are available to identify IDH1 and/or IDH2 mutations, they impose a time and cost burden on patients. We previously trained deep learning models visually differentiate IDH wild-type (IDHwt) and IDH mutant (IDHmut) gliomas in a small set of H&amp;E-stained whole image slides (WSIs) from TCGA using an Uncertainty-Aware Convolutional Neural Network (CNN) at 10x magnification. In this follow-up study, we aimed to improve our models by expanding our annotations of a more representative subset of the TCGA public data, increasing the sampling magnification to 20x, redesigning the preprocessing filters, adjusting the training pipeline to reduce overfitting, and assessing the confidence in model prediction via uncertainty metrics. METHODS By modifying the pre-processing methods from our pilot study, we increased the number of expert-annotated WSIs. Using a 2:1:2 train/validation/test split, we fine-tuned a ResNet18 deep learning model with a pre-trained feature extractor and Monte Carlo dropouts. To identify image features critical for separating by IDH status, we extracted the learned embeddings and performed post-hoc analyses (PCA, t-SNE, and UMAP). RESULTS The new set of annotations resulted in ~15-fold increase in the number of WSIs (i.e.,&amp;gt;2.5 million tiles), without any data augmentation. Our prototype model demonstrated clear separation of cases according to IDH status (sensitivity = 0.63, specificity = 0.91, weighted F1 = 0.81). CONCLUSION We successfully improved the prediction of IDH status in H&amp;E-stained WSIs and identified potential subtypes of IDHwt and IDHmut diffuse gliomas after significantly increasing the dataset size with appropriate expert annotations. We are currently addressing the data imbalance by annotating additional IDHmut glioma WSIs. Furthermore, we will integrate other biomarkers (1p19q, EGFR etc.) to increase the robustness of histo-pathomics as a surrogate for molecular tests.

PATH-39. AI-BASED IDENTIFICATION OF GLIOMA IDH MUTATIONAL STATUS FROM H&amp;E-STAINED WHOLE SLIDE IMAGES

Abstract INTRODUCTION Isocitrate-dehydrogenase (IDH) mutational status is diagnostically critical in adult gliomas, with prognostic and therapeutic implications. IDH status cannot be determined by sole histologic assessment and requires molecular testing. We hypothesize that AI-based analysis can accurately predict IDH mutational status in glioma, by retrieving sub-visual cues in H&amp;E-stained digitized tissue sections. MATERIALS AND METHODS A retrospective discovery cohort of 1,534 cases (756/778 IDH-wildtype/IDH-mutant, including all available grades) from the TCGA-LGG/TCGA-GBM collections was used for model development with 10-fold cross-validation (CV). A replication cohort of 114 cases (82/32 IDH-wildtype/IDH-mutant) from the University of Pennsylvania Health System (UPHS) was used for independent hold-out evaluation. Each 20X magnification whole slide image (WSI) underwent comprehensive curation for elimination of artifactual content, followed by partitioning into 256x256 patches, and feature extraction using pre-trained i) ImageNet weights (baseline), and ii) self-supervised vision transformer (ViT). A weakly-supervised attention-based multiple-instance-learning framework distinguished cases as IDH-wildtype or IDH-mutant, while generating visually interpretable attention heatmaps. RESULTS Evaluation on discovery and replication cohorts with the ViT yield accuracy of 90.84% (AUCDiscovery=97.16%) and 93.94% (AUCReplication=97.36%), respectively, with high sensitivity (i.e., high confidence in correctly predicting IDH-wildtype glioma). Comparison of the ViT with the baseline model on the replication cohort indicates the ViT superiority by improvements of 8% and 9.5% in accuracy and AUC, respectively. Histologic assessment of heatmaps indicates IDH-wildtype tumors exhibiting distinct regions of significant pleomorphism and microvascular proliferation, while IDH-mutant tumors exhibit dense nodular cell concentrations, microcystic architecture, and gemistocytic cells. CONCLUSION Our accurate H&amp;E-based computational determination of glioma IDH status, with interpretations aligned with human-identifiable features, can contribute to obviating the need for molecular analyses and enable expedited diagnosis even in community healthcare settings. This study robustly identifies morpho-IDH correlates and could enable expedited patient prognostic stratification.

BIOM-76. EXPLORING CSF MICRORNA SIGNATURES AS DIAGNOSTIC BIOMARKERS IN IDH-WILDTYPE DIFFUSE GLIOMAS

Abstract The most prevalent malignant tumors of the central nervous system are adult-type diffuse gliomas. Isocitrate dehydrogenase (IDH) mutations are identified in a subset of diffuse gliomas, leading to two distinct subtypes of gliomas: IDH-wildtype and IDH-mutant. In comparison to IDH-mutant gliomas, IDH-wildtype gliomas tend to be associated with a more rapid progression and lower overall survival rates. The analysis of differentially expressed microRNAs (DE-miRNAs) in cerebrospinal fluid (CSF) of IDH-wildtype diffuse gliomas could provide an effective and non-invasive approach to assist in the early diagnosis, classification, and management of the disease. Extracellular vesicle (EV)-derived miRNAs obtained from the CSF of 11 patients with IDH-wildtype diffuse gliomas and 8 controls were analyzed by microRNA sequencing (miRNA-seq). DE-miRNAs were defined using p-value≤0.05 and absolute log2 fold change (log2FC) ≥1. Candidate DE-miRNAs were validated by qRT-PCR in 24 samples (15 IDH-wildtype vs. 9 control) using the 2-ΔΔCT method, followed by receiver operating characteristic (ROC) curve analysis. Hsa-miR-24-3p was used as the internal control. miRNA-seq analysis identified hsa-miR-484, hsa-miR-223-3p, hsa-miR-1246, hsa-miR-323a-3p, hsa-miR-106b-3p, hsa-miR-21-5p, hsa-miR-15a-5p, has-miR-15b-5p, and hsa-miR-92a-3p among the top 20 upregulated miRNAs in the CSF of patients with IDH-wildtype diffuse gliomas. Further analysis by qPCR showed that patients with IDH-wildtype diffuse gliomas had significantly higher levels of has-miR-21-5p (2.28 ± 2.33) compared to control subjects (-2.22e-007 ± 1.08, p=0.012). The ROC curve analysis revealed an area under the curve (AUC) of 0.84 (95% CI, 0.68-1.0) for has-miR-21-5p CSF levels in distinguishing IDH-wildtype diffuse gliomas from control subjects. EV-derived miRNAs in CSF, including has-miR-21-5p, have the potential to distinguish IDH-wildtype diffuse gliomas from control individuals in a minimally-invasive manner and serve as diagnostic biomarkers.

STEM-12. A NEURONAL STEM-LIKE PHENOTYPE IN GRADE 4 IDH-MUTANT ASTROCYTOMA WITH CDKN2A/B LOSS IS ASSOCIATED WITH CUX2 DEFICIENCY

Abstract Diffuse gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, the loss of CDKN2A/B in IDH-mutant astrocytoma confers an aggressive high grade phenotype and is the strongest implicated molecular alteration associated poor clinical survival, thus is now sufficient to define a grade 4 tumor regardless of histologic grade. However, there remains no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with RNA sequencing data and found the increased expression of regulators of embryonic nervous system development and signaling concurrent with CDKN2A/B loss. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and cell-lines harboring CDKN2A/B homozygous deletion, we stably re-expressed p14ARF, p15INK4B, and p16INK4A using a Tet-inducible system. IDH-mutant cell lines with re-expression of p14, p15, or p16 displayed differential transcription factor activation, impaired neurosphere capability, decreased colony formation, and lower neurosphere proliferation. Intriguingly, RNA-seq data revealed CUX2, a transcription factor known to control neuronal precursor behavior, as the likely candidate regulating the differential expression profile across CDKN2A/B status. We observed increased CUX2 expression in cell lines stably re-expressing p14, p15, and p16. We validated the CUX2 signature across publicly available datasets of IDH-mutant astrocytoma where CUX2 expression negatively correlated with loss of CDKN2A/B in patient tumors. Together our work suggests CUX2 deficiency in IDH-mutant astrocytoma with CDKN2A/B deletion enables an increased neuronal stem-like phenotype in these grade 4 tumors.

Single-cell transcriptomics reveals IRF7 regulation of the tumor microenvironment in isocitrate dehydrogenase wild-type glioma.

Mutations in isocitrate dehydrogenase (IDH) are important markers of glioma prognosis. However, few studies have examined the gene expression regulatory network (GRN) in IDH-mutant and wild-type gliomas. In this study, single-cell RNA sequencing and spatial transcriptome sequencing were used to analyze the GRN of cell subsets in patients with IDH-mutant and wild-type gliomas. Through gene transcriptional regulation analysis, we identified the M4 module, whose transcription factor activity is highly expressed in IDH wild-type gliomas compared to IDH-mutants. Enrichment analysis revealed that these genes were predominantly expressed in microglia and macrophages, with significant enrichment in interferon-related signaling pathways. Interferon regulatory factor 7 (IRF7), a transcription factor within this pathway, showed the highest percentage of enrichment and was primarily localized in the core region of wild-type IDH tumors. A machine-learning prognostic model identified novel subgroups within the wild-type IDH population. Additionally, IRF7 was shown to promote the proliferation and migration of T98G and U251 cells in vitro, and its knockdown affected glioma cell proliferation in vivo. This study systematically established the regulatory mechanism of IDH transcriptional activity in gliomas at the single-cell level and drew a corresponding cell map. The study presents a transcriptional regulatory activity map for IDH wild-type gliomas, involving single-cell RNA sequencing and spatial transcriptomics to identify gene regulatory networks, machine learning models for IDH subtyping, and experimental validation, highlighting the role of IRF7 in glioma progression.

Association of immunoglobulin E levels with glioma risk and survival.

Previous epidemiologic studies have reported an association of serum immunoglobulin E (IgE) levels with reduced glioma risk, but the association between IgE and glioma prognosis has not been characterized. This study aimed to examine how sex, tumor subtype, and IgE class modulate the association of serum IgE levels with glioma risk and survival. We conducted a case-control study using participants from the University of California, San Francisco Adult Glioma Study (1997-2010). Serum IgE levels for total, respiratory and food allergy were measured in adults diagnosed with glioma (n = 1319) and cancer-free controls (n = 1139) matched based on age, sex, and race and ethnicity. Logistic regression was adjusted for patient demographics to assess the association between IgE levels and glioma risk. Multivariable Cox regression adjusted for patient-specific and tumor-specific factors compared survival between the elevated and normal IgE groups. All statistical tests were 2-sided. Elevated total IgE was associated with reduced risk of IDH-wildtype (RR = 0.78, 95% CI: 0.71-0.86) and IDH-mutant glioma (RR = 0.73, 95% CI: 0.63-0.85). In multivariable Cox regression, positive respiratory IgE was associated with improved survival for IDH-wildtype glioma (RR = 0.79, 95% CI: 0.67-0.93). The reduction in mortality risk was significant in females only (RR = 0.75, 95% CI: 0.57-0.98) with an improvement in median survival of 6.9 months (P<.001). Elevated serum IgE was associated with improved prognosis for IDH-wildtype glioma, with a more pronounced protective effect in females than males, which has implications for the future study of IgE-based immunotherapies for glioma.

Health-Related Quality of Life and Treatment Satisfaction of Patients with Malignant IDH Wild-Type Gliomas and Their Caregivers.

(1) Background: Clinical aspects like sex, age, Karnofsky Performance Scale (KPS) and psychosocial distress can affect the health-related quality of life (HR-QoL) and treatment satisfaction of patients with malignant isocitrate dehydrogenase wild-type (IDHwt) gliomas and caregivers. (2) Methods: We prospectively investigated the HR-QoL and patient/caregiver treatment satisfaction in a cross-sectional study with univariable and multiple regression analyses. Questionnaires were applied to investigate the HR-QoL (EORTC QLQ-C30, QLQ-BN20) and treatment satisfaction (EORTC PATSAT-C33). (3) Results: A cohort of 61 patients was investigated. A higher KPS was significantly associated with a better HR-QoL regarding the functional scales of the EORTC QLQ-C30 (p < 0.004) and a lower symptom burden regarding the EORTC QLQ-BN20 (p < 0.001). The patient treatment satisfaction was significantly poorer in the patients older than 60 years in the domain of family involvement (p = 0.010). None of the investigated aspects showed a significant impact on the treatment satisfaction of caregivers. (4) Conclusions: We demonstrated that in patients with IDHwt gliomas, the KPS was the most important predictor for a better HR-QoL in functional domains. Data on the HR-QoL and treatment satisfaction in patients with IDHwt gliomas and their caregivers are rare; therefore, further efforts should be made to improve supportive care in this highly distressed cohort.

Association of immunoglobulin E levels with glioma risk and survival.

Previous epidemiologic studies have reported an association of serum immunoglobulin E (IgE) levels with reduced glioma risk, but the association between IgE and glioma prognosis has not been characterized. This study aimed to examine how sex, tumor subtype, and IgE class modulate the association of serum IgE levels with glioma risk and survival. We conducted a case-control study using participants from the University of California, San Francisco Adult Glioma Study (1997-2010). Serum IgE levels for total, respiratory and food allergy were measured in adults diagnosed with glioma (n=1319) and cancer-free controls (n=1139) matched based on age, sex, and race and ethnicity. Logistic regression was adjusted for patient demographics to assess the association between IgE levels and glioma risk. Multivariable Cox regression adjusted for patient-specific and tumor-specific factors compared survival between the elevated and normal IgE groups. All statistical tests were 2-sided. Elevated total IgE was associated with reduced risk of IDH-wildtype (RR=0.78, 95% CI: 0.71-0.86) and IDH-mutant glioma (RR=0.73, 95% CI: 0.63-0.85). In multivariable Cox regression, positive respiratory IgE was associated with improved survival for IDH-wildtype glioma (RR=0.79, 95% CI: 0.67-0.93). The reduction in mortality risk was significant in females only (RR=0.75, 95% CI: 0.57-0.98) with an improvement in median survival of 6.9 months (P<.001). Elevated serum IgE was associated with improved prognosis for IDH-wildtype glioma, with a more pronounced protective effect in females than males, which has implications for the future study of IgE-based immunotherapies for glioma.

Shape matters: unsupervised exploration of IDH-wildtype glioma imaging survival predictors

Abstract Objectives This study examines clustering based on shape radiomic features and tumor volume to identify IDH-wildtype glioma phenotypes and assess their impact on overall survival (OS). Materials and methods This retrospective study included 436 consecutive patients diagnosed with IDH-wt glioma who underwent preoperative MR imaging. Alongside the total tumor volume, nine distinct shape radiomic features were extracted using the PyRadiomics framework. Different imaging phenotypes were identified using partition around medoids (PAM) clustering on the training dataset (348/436). The prognostic efficacy of these phenotypes in predicting OS was evaluated on the test dataset (88/436). External validation was performed using the public UCSF glioma dataset (n = 397). A decision-tree algorithm was employed to determine the relevance of features associated with cluster affiliation. Results PAM clustering identified two clusters in the training dataset: Cluster 1 (n = 233) had a higher proportion of patients with higher sphericity and elongation, while Cluster 2 (n = 115) had a higher proportion of patients with higher maximum 3D diameter, surface area, axis lengths, and tumor volume (p &lt; 0.001 for each). OS differed significantly between clusters: Cluster 1 showed a median OS of 23.8 compared to 11.4 months of Cluster 2 in the holdout test dataset (p = 0.002). Multivariate Cox regression showed improved performance with cluster affiliation over clinical data alone (C index 0.67 vs 0.59, p = 0.003). Cluster-based models outperformed the models with tumor volume alone (evidence ratio: 5.16–5.37). Conclusion Data-driven clustering reveals imaging phenotypes, highlighting the improved prognostic power of combining shape-radiomics with tumor volume, thereby outperforming predictions based on tumor volume alone in high-grade glioma survival outcomes. Clinical relevance statement Shape-radiomics and volume-based cluster analyses of preoperative MRI scans can reveal imaging phenotypes that improve the prediction of OS in patients with IDH-wild type gliomas, outperforming currently known models based on tumor size alone or clinical parameters. Key Points Shape radiomics and tumor volume clustering in IDH-wildtype gliomas are investigated for enhanced prognostic accuracy. Two distinct phenotypic clusters were identified with different median OSs. Integrating shape radiomics and volume-based clustering enhances OS prediction in IDH-wildtype glioma patients.

Cognitive phenotypes: Unraveling the heterogeneity in cognitive dysfunction among patients with primary brain tumors receiving radiotherapy.

Patients with primary brain tumors demonstrate heterogeneous patterns of cognitive dysfunction, which we explore using latent profile analysis (LPA) to identify cognitive phenotypes and their trajectories in patients receiving radiotherapy (RT). Ninety-six patients completed neuropsychological testing before and post-RT (3, 6, 12-months) on a prospective longitudinal trial, including measures of processing speed, executive function, language, and verbal and visual memory. Models with 2-4 classes were examined. Demographic and clinical data were examined across phenotypes and post-RT cognitive change was evaluated. The optimal model identified three unique cognitive phenotypes including a group of patients with generalized impairments (11.5%), a group with isolated verbal memory impairments (21.9%), and a group with minimal impairments (66.7%). The Verbal Memory phenotype had fewer years of education (p=.007) and a greater proportion of males (p<.001); the Generalized group had a greater proportion of patients with IDH-wild type gliomas and showed greater symptoms of anxiety and poorer quality of life (p-values<.05); and the Minimal Impairment phenotype had higher rates of IDH-Mutant gliomas. Approximately 50% of patients declined on at least one cognitive domain with memory the most vulnerable. Patients that declined reported greater symptoms of depression (p=.007) and poorer quality of life (p=.025). We identified three distinct cognitive phenotypes in patients with primary brain tumors receiving RT, each associated with unique demographic and clinical (e.g., IDH mutational status) profiles, with mood symptoms associated with late cognitive decline. This patient-centered approach enhances our understanding of clinical profiles associated with cognitive dysfunction and treatment-related neurotoxicity.