IDH Wildtype Research Articles

Differentiating Glioma Recurrence and Pseudoprogression by APTw CEST MRI.

Recurrent glioma is highly treatment resistant due to its metabolic, cellular, and molecular heterogeneity and invasiveness. Tumor monitoring by conventional MRI has shortcomings to assess these key glioma characteristics. Recent studies introduced chemical exchange saturation transfer for metabolic imaging in oncology and assessed its diagnostic value for newly diagnosed glioma. This prospective study investigates amide proton transfer-weighted (APTw) MRI at 3 T as an imaging biomarker to elucidate the molecular heterogeneity and invasion patterns of recurrent glioma in comparison to pseudoprogression (PsPD). We performed a monocenter, prospective trial and screened 371 glioma patients who received tumor monitoring between August 2021 and March 2024 at our institution. The study included IDH wildtype astrocytoma and IDH mutant astrocytoma and oligodendroglioma, graded according to the WHO 2021 classification. Patients had received clinical standard of care treatment including surgical resection and radiochemotherapy prior to study inclusion. Patients were monitored by 3 monthly MRI follow-up imaging, and response assessment was performed according to the RANO criteria. Within this cohort, we identified 30 patients who presented with recurrent glioma and 12 patients with PsPD. In addition to standard anatomical sequences (FLAIR and T1-w Gd-enhanced sequences), MRI included APTw imaging. After sequence co-registration, semiautomated segmentation was performed of the FLAIR lesion, CE lesion, resection cavity, and the contralateral normal-appearing white matter, and APTw signals were quantified in these regions of interest. APTw values were highest in solid, Gd-enhancing tumor parts as compared with the nonenhancing FLAIR lesion (APTw: 1.99% vs 1.36%, P = 0.001), whereas there were no detectable APTw alterations in the normal-appearing white matter (APTw: 0.005%, P < 0.001 compared with FLAIR). Patients with progressive disease had higher APTw levels compared with patients with PsPD (APTw: 1.99% vs 1.26%, P = 0.008). Chemical exchange saturation transfer identified heterogeneity within the FLAIR lesion that was not detectable by conventional sequences. There were also focal APTw signal peaks within contrast enhancing lesions as putative metabolic hotspots within recurrent glioma. The resection cavity developed an APTw increase at recurrence that was not detectable prior to recurrence nor in patients with PsPD (APTw before recurrence: 0.6% vs 2.68% at recurrence, P = 0.03). Our study shows that APTw imaging can differentiate PD and PsPD. We identify previously undetectable imaging patterns during glioma recurrence, which include alterations within resection cavity associated with disease progression. Our work highlights the clinical potential of APTw imaging for glioma monitoring and further establishes it as an imaging biomarker in neuro-oncology.

SLC12A9 is an immunological and prognostic biomarker for glioma

BackgroundGlioma is one of the most common malignant brain tumors. It has a high rate of progression and a poor prognosis, and effective biomarkers still need to be identified. The solute carrier family 12 (SLC12) family has been reported to be involved in various physiological and pathological processes, but their functional roles in glioma remain unclear. MethodsUsing public datasets, we studied the mutation and expression level of SLC12 family genes in glioma and identified the significantly differentially expressed member solute carrier family 12 member 9 (SLC12A9). We further predicted the prognostic role of SLC12A9 in glioma by using the Kaplan–Meier method and Cox regression analysis. Then, we performed biological functional enrichment analysis. We focused on the relationships between SLC12A9 expression and immune infiltration in glioma. Meanwhile, we conducted in vitro experiments to evaluate the effect of SLC12A9 expression on glioma cells. ResultsAmong the members of the SLC12 family, SLC12A9 had the highest mutation rate in glioma, with gene amplification as the major mutation type, and its expression was significantly upregulated in glioma. Higher SLC12A9 expression was significantly associated with older age, higher grade, wild-type isocitrate dehydrogenase (IDH), and a worse prognosis. The functional enrichment analysis indicated that SLC12A9 is mainly related to ion channel annotation. Gene set enrichment analysis (GSEA) revealed that SLC12A9 was mainly related to the DNA replication pathway. Furthermore, we found that SLC12A9 correlated with tumor-infiltrating immune cells and immune checkpoints. Thus, SLC12A9 may be involved in regulating the immune response of glioma. Finally, our in vitro experiments revealed that silencing SLC12A9 dramatically inhibited glioma cell growth and migration. ConclusionsWe showed that SLC12A9 may be a new predictive biomarker for glioma diagnosis, prognosis, and immunotherapy response, offering helpful guidelines to advance glioma treatment.

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.

TMIC-53. USE OF CEREBRAL OPEN-FLOW MICROPERFUSION TO IDENTIFY POTENTIAL ONCOMETABOLITE, L-2-HYDROXYGLUTARATE, IN GLIOBLASTOMA CHEMOTHERAPY ADAPTATION

Abstract Glioblastoma (GBM) is among the most prevalent and lethal brain tumors, comprising nearly half of all central nervous system malignancies and imparting a median overall survival of only 18-20 months. One major challenge in curing this disease is the limited understanding of how GBM cells biologically respond to treatments like radiotherapy and chemotherapy, including temozolomide (TMZ), in real-time. A significant challenge is observing changes within the tumor interstitial fluid (ISF), which mediates adaptive intercellular signaling between tumor cells and their surrounding tumoral and stromal neighbors. Microfluidic sampling methods, such as cerebral microdialysis and microperfusion, have started to provide valuable insights into the ISF signaling dynamics. These methods enable real-time biomolecular monitoring of this often-neglected component of the tumor microenvironment (TME). We have performed in vivo cerebral open-flow microperfusion (cOFM) pilot studies to identify metabolomic and proteomic changes within the tumor ISF resulting from differential treatment with either TMZ or vehicle control. Among these metabolite and protein changes, we identified an increase in 2-hydroxyglutarate (2-HG). While D-2-HG is a hallmark metabolite of isocitrate dehydrogenase mutant (IDH-mut) tumors, our model utilized the IDH wild-type (IDH-WT) CT2A mouse-syngeneic glioma model. Subsequent analysis of enantiomeric confirmation characterized this to be predominantly L-2-HG. Follow-up in vitro studies have shown that elevated L-2-HG plays a functional role in IDH-WT patient-derived glioma cells via non-canonical HIF1α stabilization and subsequent expression of HRE genes. This suggested that L-2-HG may play a similar role in IDH-WT GBM as D-2-HG plays in IDH-mutant tumors. This study demonstrates the potential of L-2-HG to function as a chemo-responsive oncometabolite in the TME of highly aggressive IDH-WT glioblastoma. By targeting the metabolic and signaling properties of L-2-HG, it may be possible to prevent chemo-resistant adaptations mounted by GBM cells when treated with TMZ.

NIMG-21. EARLY-STAGE GLIOBLASTOMA AND MOLECULAR ANALYSIS REVEAL THE RADIOLOGICAL INITIATION OF IDH WILDTYPE GLIOBLASTOMA

Abstract Glioblastoma (GB), IDH wildtype, is an aggressive and malignant tumor that necessitate early surgical intervention upon radiological suspicion. Consequently, the natural growth dynamics of GB remain not fully understood. Previous studies have examined GB growth using multiple MRIs between initial radiological diagnosis of GB and preoperative MRI, but these studies have short-term intervals between MRIs (defined as shortGB-cohort). Unless GB growth is a constant phenomenon, shortGB cannot estimate radiological initiation. In this study, we focused on early-stage GB (eGB), characterized by small, nonspecific lesions on MRI that eventually progress to classic GB findings. We compared three cohorts: 49 cases of eGB. 68 cases of shortGBt, and 23 cases of eGB from previous publications (other-eGB). Molecular analyses revealed that TERT promoter mutations, EGFR amplification/gain, CDKN2A hemi/homozygous deletion, and PTEN hemi/homozygous deletion were consistent between eGB and shortGB. Our analysis indicated that the radiological initiation of GB in eGB was -0.84 years (95% confidence interval (CI): -1.09 to -0.68), compared to -0.35 years (95%CI: -0.46 to -0.28) in shortGB. In eGB, factors such as age &amp;lt; 65, MIB1 &amp;gt; 30%, TERTp mutation, and the presence of copy-number alterations (CNA) in EGFR/PTEN/CDKN2A, with or without TERTp mutation, correlated with faster tumor progression. In cases without these alterations, the estimated radiological initiation was -2.31 years (95%CI: -100 to -0.80), indicating slower progression. The ShortGB-cohort did not show any significant changes based on these factors, suggesting it does not actually reflect tumor origin. The other-eGB cohort presented radiological initiation between -0.92 and -0.15 year, consistent with our eGB-cohort. This study investigates the radiological origin of GB using extremely rare cases of eGB, providing insights into the radiological pathophysiology and its association with molecular alterations in IDH-wildtype GB.

CNSC-54. CENTRAL AND BOUNDARY-DRIVEN GROWTH PATTERNS DOMINATE RESPECTIVELY IDH WILD-TYPE AND MUTANT GLIOMAS

Abstract Diffuse gliomas are the most prevalent primary malignant brain tumors in adults and are characterized by invasive growth and poor prognosis. Tumor cells infiltrate the brain parenchyma and spread to distant sites. The aim of this study is to characterize the spatial heterogeneity, mode, and direction of tumor development to identify key areas for localized treatment. Neuronavigation was employed to collect n=134 image-guided samples from n=16 adult patients with diffuse gliomas, including n=7 IDH wild-type (IDHwt) and n=9 IDH mutant (IDHmut) tumors from regions with and without MRI abnormalities. Collected samples were subjected to targeted and shallow whole-genome sequencing. Somatic variants were used to determine the evolutionary processes governing heterogeneity. Examination of the dN/dS ratio, Tajima’s D score, and MOBSTER model suggested that all tumors are consistent with neutral evolution, as previously reported. Considering that genetic heterogeneity was a result of stochastic mutations, we used phylogeographic relationships between samples to dissect the spatiotemporal development of these tumors. Evolutionary (patristic) and cartesian (Euclidean) distances between sample pairs from the same patient were correlated in n=2/9 IDHmut and n=2/7 IDHwt patients, suggesting that migratory or punctuated evolutionary processes play a major role in tumor diffusion. An examination of spatial diffusion revealed that the latest descendant appeared peripherally in n=5/9 IDHmut patients, suggesting boundary-driven growth. In the remaining cases, three patients exhibited centrally-driven growth, whereas a fourth patient displayed a mixed pattern. In contrast, in n=4/7 IDHwt patients, descendants appeared closer to the tumor center, suggesting centrally-driven growth. In the remaining three IDHwt patients, one patient showed a diffusion that was consistent with boundary-driven growth, while the other two patients showed a mixed pattern. Taken together our data suggest that IDHwt tumors tend to develop centrally, whereas IDHmut tumors preferably develop outward. Our data could aid in tailoring localized treatment based on projected growth patterns.

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.

INNV-14. OUTCOMES OF PATIENTS WITH ISOCITRATE DEHYDROGENASE-MUTANT WHO GRADE 4 ASTROCYTOMA TREATED WITH TUMOR TREATING FIELDS (TTFIELDS) THERAPY: A REAL-WORLD ANALYSIS

Abstract BACKGROUND Tumor Treating Fields (TTFields) therapy is approved for the treatment of patients with newly diagnosed glioblastoma, based on the EF-14 study which demonstrated improvement in progression free survival and overall survival (OS). EF-14 included patients with the isocitrate dehydrogenase (IDH) mutation (IDHmut), which has since been reclassified as IDHmut WHO grade 4 astrocytoma (Astrocytoma IDHmut/G4) and confers a more favorable prognosis than IDH wild type. However, large real-world datasets are lacking. Here, we report real-world outcomes of patients with Astrocytoma IDHmut/G4 treated with TTFields in the US. METHODS Utilizing electronic health records from the xCures real-world data platform, patients with newly diagnosed Astrocytoma IDHmut/G4 receiving TTFields in the US from January 1 to December 31, 2019 were analyzed and IDH-mut status was confirmed. Survival was analyzed based on IDH-mut status and TTFields usage, with patients categorized into 2 usage groups (minimum 30 days treatment): high (≥50%) and low (&amp;lt;50%) usage. RESULTS Among 1285 patients with known IDH status, 82 had an IDH-mut and were included. The median (range) age of patients was 40.6 (21–75) years, with the majority being men (n=58/71%) and with methylguanine-methyltransferase-promoter methylation (n=48/59%). Median TTFields therapy duration and usage were 9.4 months and 76.8%, respectively. OS at 2 and 4 years was 66% (95% CI: 56–77%) and 44% (34–57%), respectively. Patients with high TTFields usage had increased OS compared to low usage (HR: 0.53 [0.28–1.02], P=0.057, n=80). Among 22 patients with a minimum 4 years of survival, 5 were still on therapy as of the data cutoff. CONCLUSIONS These findings demonstrate the utility of the xCures platform in systematically assessing outcomes for a rare glioma subtype in the real-world setting, and suggests that patients with Astrocytoma IDHmut/G4 may benefit from TTFields therapy. Additional patient follow-up and correlative data will be presented.

SURG-52. LEPTOMENINGEAL DISSEMINATION AFTER GAMMATILE AND LITT IN HIGH GRADE ASTROCYTOMA PATIENTS

Abstract PURPOSE To present a case series of leptomeningeal dissemination after localized treatment with GammaTile or laser interstitial thermal therapy (LITT) in patients with high grade astrocytoma. BACKGROUND Leptomeningeal dissemination occurs primarily in glioblastoma patients with prolonged survival and those who undergo aggressive treatment courses. Targeted therapies such as GammaTile (which contains cesium-131 radiation-emitting seeds) or LITT may provide localized disease control following recurrence and serve as an immediate treatment modality for patients with recurrent disease in the weeks leading up to radiotherapy or systemic treatment. METHODS We retrospectively reviewed all consecutive patients with high grade astrocytoma treated with GammaTile or LITT who were found to have leptomeningeal dissemination of disease. Histological diagnosis, NGS and immunohistochemistry of tumor tissue were performed at both original diagnosis and at time of GammaTile placement or LITT procedure. Leptomeningeal dissemination was diagnosed through MRI findings on brain and spine. Cases were analyzed for time to development of leptomeningeal dissemination, median overall survival, survival from time of leptomeningeal dissemination diagnosis, time of dissemination to second radiation therapy. Tumor location, MGMT status and other molecular markers were also reviewed. RESULTS Out of 90 high grade astrocytoma patients treated with gamma tile radiation, 4 progressed to exhibit disseminated disease. There were 2 female patients, mean age was 50 years. Location of tumor was in the left temporal lobe in 3 patients and right temporal in 1. They were all IDH wild type. Two were MGMT methylated, two were non methylated. The median time from initial glioma diagnosis to LMD was 221 months (range 11-152) and overall survival after disseminated disease diagnosis was 7.5 weeks (range 3–13). CONCLUSION Leptomeningeal dissemination is a devastating complication of aggressive gliomas. Currently, there is no standard treatment for disseminated disease in high grade astrocytoma patients. Systemic therapy is needed following localized therapies to control disease. Further research into new therapies is needed to allow for better outcomes.

CTIM-09. INB-200: FULLY ENROLLED PHASE 1 STUDY OF GENE-MODIFIED AUTOLOGOUS GAMMA-DELTA (ΓΔ) T CELLS IN NEWLY DIAGNOSED GLIOBLASTOMA MULTIFORME (GBM) PATIENTS RECEIVING MAINTENANCE TEMOZOLOMIDE (TMZ)

Abstract IN8bio’s DeltEx drug resistant immunotherapy (DRI), comprising TMZ-resistant γδ T cells engineered to express methylguanine-DNA methyltransferase (MGMT), enables γδ T cells to target upregulated NKG2D ligands on tumor cells in real time during alkylating chemotherapy exposure. Updated results from the fully enrolled Phase 1 trial evaluating DRI in adult newly diagnosed GBM subjects with IDH wild type and mutant tumors, adequate organ function and KPS ≥ 70%. Cohorts (C) 1, 2 and 3 received 1, 3 or 6 doses (1 x 107 DRI cells/dose) into the resection cavity with 150 mg/m2 of IV TMZ on Day 1 of each of 6 Stupp maintenance cycles. The primary endpoint is safety and secondary endpoints include survival; immunologic correlative analyses are included. Dose limiting toxicities (DLTs) are defined as treatment related ≥ grade (G) 3 cardiopulmonary or hepatic toxicity, G4 toxicity exceeding 72 hours or neurologic deterioration that exceeds 2 weeks. A total of 23 subjects were enrolled and 13 dosed (61% male; median age 68 (range: 21-74); 92% IDH-WT, 54% MGMT unmethylated). No DLTs, cytokine release syndrome (CRS), neurotoxicity (ICANS) or treatment related deaths were reported. The most common adverse events were decreased WBC/platelet count, asthenia, fatigue, hydrocephalus, headache, decreased appetite, urinary tract infection, thrombosis and balance disorder with ≥G3 platelet count decreased in 23% and WBC/ neutrophil/ lymphocyte count decreased in 7.7% each. Peripheral TMZ-based lymphodepletion was maintained for up to 1 year evidenced by near or below normal range T, B, and NK subsets. With median follow-up of 10.8 months, 83% of subjects exceeded the median 7 month Progression Free Survival (PFS) of the Stupp regimen alone, had manageable toxicity with a continued encouraging trend in PFS. Subject with IDH mutant tumor remains progression free for &amp;gt; 35 months. Long-term follow-up for durability of PFS and OS continues.

QLTI-04. UPDATE ON HIGH-GRADE GLIOMA PATIENTS TREATED WITH TTFIELDS FROM NANFANG HOSPITAL IN CHINA

Abstract OBJECTIVE Tumour-treating fields (TTFields) have changed the first-line clinical practice of glioblastoma worldwide due to their promising therapeutic efficacy. The aim of this study was to investigate the clinical efficacy of TTFields therapy for HGG in Nanfang Hospital, China. In 2023 ASNO we reported PFS.Now we reporte update about OS from our single center study. METHODS From January 2019 to December 2022, a total of 25 patients with newly diagnosed HGG (ndHGG) treated with TTFields were retrospectively included in our study. Among these patients, 9 patients received concurrent radiochemotherapy in combination with TTFields and 16 patients received non-concurrent chemoradiotherapy in combination with TTFields. The primary endpoint of the study was mPFS and mOS (Kaplan-Meier method used to estimate PFS and OS survival curves). Secondary endpoint was the influences about KPS score in PFS and OS. RESULTS The 25 ndHGG patients treated with TTFields included nine males and sixteen females with a mean age of 47.1 years (12-68). Gross total resection (GTR) was performed in eighteen patients. Twenty-one patients were IDH wild type, eleven patients showed methylation of the MGMT promoter. Followed up until January 2024, the median PFS was 13.3 months [95% CI: 11.33-15.2] with TTFields combined and 4.0 months (95% CI, 3.8-4.4) without TTFields treatment in EF-14.Median OS was 26.53 months [95% CI:19.47-33.57] with TTFields and 16.0 months (95% CI, 3.8-4.4) control in EF-14. In the KPS stratification, OS was 27.5 months (95% CI: 22.95-32.1) vs 4.3 months (95% CI: 0-11.2), p=0.0001. The OS of patients with concurrent chemoradiotherapy combined with TTFields vs. without concurrent chemoradiotherapy combined with TTFields was 26.5 months (95% CI: 24.33-28.7) vs 21.2 (95% CI: 3.1-39.3) months, p=0.59. CONCLUSIONS TTFields therapy is an effective treatment for HGG. In this study the addition of TTFields resulted in a statistically significant improvement in PFS and OS.

TMIC-19. EXCESSIVE LIPID PRODUCTION SHAPES GLIOMA TUMOR MICROENVIRONMENT

Abstract Disrupted lipid metabolism is a characteristic of gliomas. This study utilizes an ultrastructural approach to characterize the prevalence and distribution of lipids within gliomas. This study made use of tissue from IDH1 wild type (IDH1-wt) glioblastoma (n=18) and IDH1 mutant (IDH1-mt) astrocytoma (n=12) tumors. We uncover a prevalent and intriguing surplus of lipids. The bulk of the lipids manifested as sizable cytoplasmic inclusions and extracellular deposits in the tumor microenvironment (TME); in some tumors the lipids were stored in the classical membraneless spheroidal lipid droplets (LDs). Frequently, lipids accumulated inside mitochondria, suggesting possible dysfunction of the beta-oxidation pathway. Additionally, the tumor vasculature has lipid deposits in their lumen and vessel walls; this lipid could have shifted in from the tumor microenvironment or have been produced by the vessel-invading tumor cells. Lipid excess in gliomas stems from disrupted beta-oxidation and dysfunctional oxidative phosphorylation pathways. The implications of this lipid-driven environment include structural support for the tumor cells and protection against immune responses, non-lipophilic drugs, and free radicals.

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.

IMMU-45. MYELOID-ASSOCIATED WILD-TYPE IDH1 PROMOTES IMMUNOSUPPRESSION IN GLIOBLASTOMA

Abstract Tumor-associated myeloid cells (TAMCs) promote immunosuppression in the GBM tumor microenvironment (TME) and resistance to immune checkpoint therapy (ICT). However, the metabolic and epigenetic mechanisms underlying TAMC activation and the therapeutic potential of fine-tuning TAMC activation remain largely unexplored. Our analyses of GBM patient single-cell RNA sequencing (scRNA-Seq) datasets demonstrated that in addition to tumor cells, wild-type isocitrate dehydrogenase (wt-IDH1) is also highly expressed in TAMCs. Using a murine model with myeloid cell-specific deletion of wt-IDH1 (LysM-cre-ERT2; wt-IDH1L/L), we demonstrated that the loss of wt-IDH1 promoted inflammatory myeloid phenotypes, increased CD8+ T cells in the TME, improved survival of GBM tumor-bearing mice, and enhanced anti-tumor effects of PD1 checkpoint blockade. Further, the pharmacological inhibition of wt-IDH1 using systemic administration of a first-in-class wt-IDH1-specific, brain-penetrant small molecule inhibitor or intrathecal delivery of siRNA targeted to wt-IDH1 mirrored the functional phenotype of wt-IDH1-deleted myeloid cells, overcame ICT resistance, and promoted long-term survival and anti-tumor immune memory. Mechanistically, in myeloid cells, the genetic or pharmacological inactivation of wt-IDH1 inhibited oxidative phosphorylation, reduced myeloid cell proliferation, increased their tumoricidal activity, and altered chromatin accessibility of key transcription factors implicated in the regulation of myeloid cell states, including AP-1, IRFs, STAT1/2, NFATs, and CEPBPs. These studies define wt-IDH1 as a metabolic checkpoint of myeloid cell activation and credential the inhibition of wt-IDH1 as a novel immunotherapeutic strategy to increase ICT efficacy for patients with GBM.

CNSC-48. DIFFERENTIAL GENE EXPRESSION UNDERLYING EPILEPTOGENICITY IN PATIENTS WITH GLIOMAS

Abstract BACKGROUND Seizures are a common sequela for patients suffering from gliomas. Molecular properties are known to influence the initiation of seizures that may influence tumor growth. Different levels of gene expression associated with seizures related to gliomas remain unclear. We analyzed RNA sequencing of gliomas to further probe these differences. METHODS Total RNA sequencing was obtained from The Cancer Genome Atlas - Lower Grade Glioma project, comprised of 2021 WHO classification low grade gliomas, including IDH-mutant and IDH-wild type, to distinguish differential expression in patients who did and did not experience seizures. Utilizing QIAGEN Ingenuity Pathways Analysis, we identified canonical and functional pathways to further characterize differential expression. RESULTS Of 289 patients with gliomas, 83 (28.7%) had available information regarding seizure occurrence prior to intervention and other pertinent variables of interest. Of these, 50 (60.2%) were allocated to the seizure group. When comparing the level of RNA expression from these tumors between the seizure and non-seizure groups, 52 genes that were significantly differentially regulated were identified. We found canonical pathways that were altered, most significantly RhoGDI and Semaphorin Neuronal Repulsive signaling. Functional gene analysis revealed tumors that promoted seizures had significantly increased functional gene sets involving neuronal differentiation and synaptogenesis. CONCLUSIONS In the setting of gliomas, differences in tumor gene expression exist between individuals with and without seizures, despite similarities in patient demographics and other tumor characteristics. There are significant differences in gene expression associated with neuron development and synaptogenesis, ultimately suggesting a mechanistic role of a tumor-neuron synapse in seizure initiation.

CTNI-57. REAL-WORLD EVIDENCE OF THE FREQUENCY OF POST-SURGICAL INITIAL OBSERVATION IN PATIENTS WITH IDH-MUTANT GLIOMA

Abstract BACKGROUND After initial resection of IDH-mutant gliomas, initial observation is an option for low-risk patients, to postpone potential therapy-related toxicities without impacting survival. Since NCCN guidelines for risk stratification are considered controversial, we aimed to assess the frequency of initial observation in IDH-mutant gliomas using real-world evidence in the US. METHODS We evaluated Optum claims from 2016-2021 of patients age ≥12 with ICD-10 codes for incident glioma. Since ICD-10 does not distinguish IDH-mutant from IDH-wild type (GBM) gliomas, we excluded patients with factors indicative of GBM (age&amp;gt;60/ hypofractionated RT/ carmustine wafer/ tumor-treating fields) to create a baseline cohort. We then evaluated the subgroup age &amp;lt;40 (&amp;lt;40 cohort), who have higher IDH-mutant incidence. To distinguish initial observation from surgical recovery, we assessed time from index surgery to first intervention. When 90% of first interventions had occurred those still without intervention were considered to undergo initial observation. RESULTS The baseline and &amp;lt;40 cohorts comprised 5404 and 646 patients, respectively. In the baseline cohort, 56% had intervention by day 90 (most commonly concurrent chemoradiation); peak intervention rate was 60%. Initial observation rate was 44%. In the &amp;lt;40 cohort, 47% had an intervention by day 90; peak intervention rate was 52%. Initial observation rate was 53%. CONCLUSIONS In both cohorts ≥90% of patients with likely IDH-mutant gliomas not initiating treatment within 3 months post-surgery continued in active observation. Initial observation rates were 44-53%, well above the levels we had expected based on NCCN guidelines. The cohorts likely include some GBM patients, for whom observation is unaccepted, and therefore these rates may understate actual initial observation rates for IDH-mutant glioma patients. These findings suggest that clinicians and patients have chosen initial observation over existing treatments, evincing a need for additional treatment options for this younger group of patients with considerably long life expectancy.

EPCO-07. INTEGRATING SPATIALLY RESOLVED MULTI-OMICS DATA TO UNCOVER DYSFUNCTIONAL METABOLISM DRIVEN NETWORKS THAT ENHANCE INFILTRATION OF DIFFUSE GLIOMAS

Abstract BACKGROUND Diffuse infiltration is an aggressive feature of high-grade gliomas with survival implications. The contribution of crosstalk between non-neoplastic and neoplastic cells to tumor infiltration remains largely understudied due to the lack of profiling techniques that retain spatial information. Spatial multi-omic profiling is a promising approach to comprehensively analyze transcript-omics, prote-omics and metabol-omics on the same tissue section while preserving information about the spatial organization of cells. Integration of these spatial studies allows for inferring the consequences of complex cell-cell communication underlying tumor infiltration. We hypothesize that the glioma edge is enriched with pro-infiltration ligands-receptors driving tumor infiltration. Strategies that disrupt these ligand-receptor networks may suppress glioma infiltration and improve clinical outcomes. METHODS We utilized a glioma tissue micro-array (TMA) to establish the neoplastic and non-neoplastic heterogeneity in the GBM infiltration edge. Each TMA slide consists of pathologist annotated tumor core and edge samples of Glioblastoma (IDH Wildtype, WHO Grade 4; n=10), Diffuse Astrocytoma (IDH Mutant, WHO Grade 3; n=3), Oligodendroglioma (IDH mutant, WHO Grade 2; n=5) and 2 non-brain control samples. We performed spatial multi-omics profiling on adjacent sections of the TMA using 10x Xenium spatial transcriptomics, imaging mass cytometry (IMC) and mass spectrometry imaging (MSI). Integration, visualization, and quantification of the spatial data was done on VisioPharm. RESULTS In GBM, we identified candidate mRNA transcripts and proteins for ligands enriched at the infiltrating edge (compared to tumor core; p&amp;lt;0.0001) that correlated with a poor progression free survival (PFS; r2=0.22). These candidate ligands were also significantly enriched at the edge of oligodendroglioma WHO Grade 2 and astrocytoma WHO Grade 3. CONCLUSIONS Spatial multi-omics profiling on a TMA consisting of Glioma WHO grades 2-4 identified differentially expressed and targetable pro-tumor infiltration ligands associated with lower PFS in GBM. Functional studies to uncover the role of metabolites enriched at the glioma edge for the expression of the identified pro-infiltration ligands are ongoing.

NCOG-40. RARE ADVERSE EFFECT OF TEMOZOLOMIDE IN A 65-YEAR-OLD FEMALE WITH GLIOBLASTOMA MULTIFORME: A CASE REPORT

Abstract BACKGROUND Temozolomide, an antineoplastic agent is primarily used to treat certain brain tumors, including glioblastoma multiforme (GBM). Common side effects include nausea, vomiting, constipation, loss of appetite, alopecia (hair loss), headache, fatigue, convulsions and rash. A rare (less than 1%) adverse effect includes aplastic anemia refractory to treatment. Herein we present a case of Temozolomide induced severe bone marrow suppression in a 65-year-old woman with GBM refractory to any treatment CASE PRESENTATION A 65-year-old female presented with dizziness and left-hand numbness. Imaging revealed a right hemisphere mass and she underwent partial resection with pathology showing GBM, IDH wildtype, with CDKN2A/B deletion. She was started on radiation therapy with concurrent temozolomide. After nearly 5 weeks of temozolomide/RT, she developed severe thrombocytopenia/neutropenia with onset of neutropenic fever and severe CMV infection, leading to her demise within a week. DISCUSSION Life threatening refractory cytopenias is a very rare side effect of Temozolomide with a high rate of morbidity/mortality. In the case of our patient, she initially had weekly CBC’s which were stable and hence was switched to a monthly schedule. The patient’s ANC and platelets showed a precipitous drop within a month and ended up with aplastic anemia. The development of this rare complication underscores the importance of increased awareness about this often-fatal adverse event and possibly more frequent monitoring to recognize it early, especially in these patients with an already limited life expectancy. A more tailored approach to monitoring blood work may be needed depending on patient factors. CONCLUSIONS Aplastic anemia refractory to treatment is a rare and life threating adverse effect of temozolomide. The frequency of checking blood work for patients on Temodar has not been definitively established with protocols ranging from once weekly to monthly. Given the potential for this fatal adverse event, it is important to develop better tools to help identify patients in whom more frequent monitoring may be necessary.

EPID-02. BLOOD-BASED CLASSIFICATION OF IDH-STATUS OF NON-ENHANCING GLIOMAS: A MACHINE LEARNING APPROACH

Abstract BACKGROUND Non-invasive determination of IDH mutational status in patients with glioma could offer significant therapeutic opportunities. While IDH wildtype (WT) tumors typically show enhancement on MRI, IDH mutant (MUT) tumors often lack this enhancement. However, relying solely on anatomic radiology may lead to misclassification, and currently, tissue acquisition is the primary method for assessing IDH-status in gliomas. These limitations hamper the development of neoadjuvant or intraoperative therapeutic strategies based on IDH-status; thus, more minimally invasive methods to determine IDH-status are needed. In this study, we assessed peripheral immune cell proportions, which vary by glioma subtype, from pre-surgery peripheral blood samples as an alternative method of classifying the IDH-status in gliomas without enhancement. MATERIALS AND METHODS We employed a highly accurate large language model (GPT-4-Turbo-128k) with over 99% accuracy to read radiology notes and exclude patients with enhancing gliomas. Then, we identified 12 immune cell subtypes from whole blood using deconvolution algorithms based on DNA methylation data. These immune cell subtypes, along with patient age, were integrated into a machine learning model (random forest) to predict IDH-status (WT vs. MUT), leveraging conditional Generative Adversarial Networks to generate synthetic data and mitigate bias in the datasets. Two independent datasets were included for training and validating the model. RESULTS The random forest model had an AUC of 0.90 and accurately identified IDH-status in 81% of a training set of 287 gliomas (65 WT and 222 MUT at varied time points after diagnosis). In an independent validation data set of 99 gliomas (6 WT and 93 MUT) from pre-surgery blood samples, the AUC was 0.93, and accurately predicted IDH-status in 92% of cases with a sensitivity of 93% and specificity of 83%. CONCLUSIONS We predicted the IDH-status of non-enhancing gliomas using patients’ age and immunomethylomic data from pre-surgical peripheral blood samples. This minimally invasive approach is a promising step toward reducing risk and enabling earlier therapies based on IDH-status.