IDH-mutant Gliomas Research Articles

ANGI-05. CDKN2A/B HOMOZYGOUS DELETION IN IDH-MUTANT ASTROCYTOMA ALTERS TUMOR CELL INVASION AND VASCULAR FORMATION

Abstract High-grade 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, molecular profiling has identified additional alterations in lower grade gliomas that confer an aggressive high-grade phenotype and a worse clinical prognosis. Of these, the loss of CDKN2A/B in IDH-mutant astrocytoma is the strongest implicated alteration and is sufficient to define a grade 4 tumor regardless of histologic grade. However, there remain 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 whole exome and RNA sequencing data and found several candidate genes/pathways regulated concurrent with CDKN2A/B loss, including regulators of embryonic development, extracellular matrix organization and regulation of vascular processes. Moreover, we identified 1 tumor that displayed intratumoral heterogeneity of CDKN2A/B expression across biopsies. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and established cell-lines harboring CDKN2A/B homozygous deletion, we then stably re-expressed cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed their decreased proliferation as compared to parental lines. IDH-mutant cell lines with re-expression of p14, p15 or p16 were characterized by differential transcription factor activation and distinct vascular formation patterns as compared to parental lines. These lines also displayed an increased cell migration and invasive potential and were associated with enhanced integrin signaling through integrin beta-3. Together, our work supports a hypothesis of regional tumor evolution with distinct biologic phenotypes across IDH-mutant gliomas.

NCMP-15. AMYLOID-BETA AND TAU-PATHOLOGY IN THE GLIOMA VICINITY

Abstract With aging societies the incidences of brain cancer and neurodegenerative disease are increasing. Although biological associations were suggested between glioma and Alzheimer's disease (AD), the rate of comorbidity is ill-defined. We here screened the tumor-adjacent cortex of a representative patient cohort for tau and Amyloid-beta deposits and correlated the results with imaging biomarkers. A total of 290 patients (37 astrocytoma, IDH-mutant, CNS-WHO grades 2-4, median-age: 39; 48 oligodendroglioma, IDH-mutant and 1p-19q-co-deleted, CNS-WHO grades 2-3, median-age: 50; 205 glioblastoma, IDH-wildtype, median-age: 65) were included. Whole-slide quantifications were performed using a digital pathology pipeline based on Matlab and QuPath codes. For a subset of 48 patients with glioblastoma 280 longitudinal MRI volumes were available for segmentation and volumetric analysis of tumor ipsi- and contralateral hippocampuses. Overall, 160 patients (55%) displayed Amyloid-beta and/or tau-pathology in tumor-adjacent cortex. AD protein deposits correlated significantly with age (p< 0.001), and showed topographic variability across brain regions. Amyloid-beta plaques were commonly observed in the occipital cortex in glioblastoma (50%, n= 10/20), while tau-pathology was commonest in the temporal lobe in both IDH-mutant and -wildtype tumors (71%, n= 10/14; 56% n= 44/79). Remarkably, isolated tau-pathology was more prevalent in IDH-mutant glioma (48% vs. 18%, p< 0.001, median age: 45). Median cell density in tumor-infiltrated cortex was highest in glioblastoma (1895 cells/mm²), and associated with reduced neuronal counts and AD protein deposits (p< 0.001). In glioblastoma, hippocampal atrophy correlated with AD-type pathology at time of diagnosis and remained stable during follow-up in the majority of patients. In sum, our data suggests frequent co-morbidity of glioma and AD-type pathology, which increases with age. Isolated tau-pathology was more pronounced in IDH-mutant tumors. In tumor-adjacent cortex, increased tumor cell infiltration paralleled neuronal loss and diminished AD-type pathology.

IMMU-57. EFFECT OF THE ONCOMETABOLITE D2HG ON MYELOID-DERIVED SUPPRESSOR CELL POPULATIONS

Abstract Mutations in the isocitrate dehydrogenase 1/2 (IDH1/2) enzyme correlate with better prognosis of gliomas, partly due to enhanced infiltration of nonimmunosuppressive granulocytic cells compared to IDH wild-type (IDHwt) tumors. Altered cytokine/chemokine secretion from tumor cells and reprogramming of myeloid cell metabolism are among the factors that drive differences in immune profiles of IDHwt vs. IDHmut tumors. IDH mutant protein produces the oncometabolite D-2-hydroxyglutarate (D2HG) instead of the canonical alpha-ketoglutarate (αKG), a co-factor for histone and DNA demethylases. Since D2HG is known to be secreted into the tumor microenvironment (TME), we interrogated the effect of this metabolite on the epigenetic landscape and behavior of granulocytic and monocytic myeloid-derived suppressor cells (g/mMDSCs). Co-culturing bone marrow cells with either IDHmut or IDHwt glioma cells demonstrated that mMDSCs, which we previously showed to be the abundant tumor infiltrating MDSC subtype in IDHwt tumors, but not gMDSCs specifically experience higher levels of apoptosis when exposed to IDHmut cells. Treatment of bone marrow cells with physiologically relevant concentrations of either D2HG or αKG demonstrated that D2HG re-capitulates the pro-apoptotic effect on mMDSCs. Furthermore, co-cultures of IDHmut glioma cells and bone-marrow cells induced a pronounced increase in global methylation on mMDSCs specifically, and we observed that mMDSCs and gMDSCs differentially express histone demethylases via western blotting. Collectively, these results suggest that D2HG can differentially impact mMDSC vs gMDSC biology by epigenetic reprogramming. Future studies will elucidate the specific targets of D2HG in mMDSCs that renders these cells more susceptible to apoptosis with the goal of identifying the mechanisms that can be modulated to down-regulate mMDSC infiltration and/or survival within the TME.

CTNI-19. RESECTION AND CESIUM-131 RADIATION SOURCES IMBEDDED IN BIO-RESORBABLE COLLAGEN TILES (GAMMATILE™) FOLLOWED BY THE STUPP PROTOCOL IN NEWLY-DIAGNOSED GLIOBLASTOMA: GESTALT TRIAL-IN-PROGRESS UPDATE

Abstract OBJECTIVE To evaluate the safety and feasibility of combining resection with immediate initiation of radiation and subsequent Stupp protocol in newly-diagnosed glioblastoma (GBM). BACKGROUND Rapid early local progression (REP) after resection, prior to the initiation of EBRT+/-chemotherapy, occurs in 25-50%. This high-rate of REP supports initiation of an effective postoperative treatment as early as safely possible. Bio-resorbable collagen tiles with imbedded cesium-131 radiation sources (Gammatiles™) are FDA cleared for this use. Intraoperatively, tiles are placed within the resection bed, thus achieving an immediate initiation of surgically targeted radiation therapy (STaRT). DESIGN/ METHODS GESTALT is a single-arm 61 patient multi-center trial. Consented adults with suspected or confirmed GBM undergo a maximum safe resection with Gammatile™ (STaRT). Patients with molecular GBM (WHO 2021 criteria) start concurrent EBRT/Temozolomide beginning 25±4 days post-surgery. Subsequent EBRT (20 fractions, 4 weeks) to low and high-risk PTV takes Gammatile™ dose into account to a combined biologically equivalent dose of 46 and 60 Gy delivered in 2Gy/fraction, respectively. Adjuvant TMZ (6 cycles) begins 28±7 days after EBRT/Temozolomide. TTF is allowed. IDH-mutated gliomas are followed for safety. Outcomes include feasibility of incorporating Gammatile™ without delay of Stupp protocol, consent/attrition rates, safety, performance status trajectory (ECOG, KPS), immune competence (absolute lymphocyte counts), local control, PFS, and OS. RESULTS The trial opened in Fall 2022 at 4 sites. 12 additional sites are onboarding (NCT05342883). 16 patients are on trial as of abstract submission. Currently, this trial appears feasible and without any unexpected intolerances/toxicities. CONCLUSIONS This is the first trial in newly diagnosed GBM patients to combine resection, Gammatile™, and the Stupp protocol, in an attempt to reduce REP, as well as possibly, improve other outcomes. RESULTS will inform the routine and investigational use of Gammatile™, and if suggestive, will form the basis for a subsequent randomized trial.

CTIM-05. RESULTS OF SAFETY LEAD IN OF PHASE II TRIAL OF COMBINATION OLAPARIB, TEMOZOLOMIDE, AND PEMBROLIZUMAB FOR PATIENTS WITH IDH-MUTANT GLIOMA

Abstract BACKGROUND Recurrent gliomas are universally fatal with few adequate treatment options. IDH-mutant gliomas may be susceptible to PARP inhibition, thus combination therapy using alkylating agents and checkpoint inhibition could be synergistic. METHODS This is an open label, phase II study of olaparib, temozolomide, and pembrolizumab for patients with recurrent IDH-mutant glioma, grade 2 or 3, with measurable enhancing disease per RANO. Patients received pembrolizumab 200mg IV on day 1 of each 21-day cycle. Oral olaparib 200mg twice daily and temozolomide 50mg/m2 daily were given days 1-7 of cycles 3-11. Here, we report the results of our safety lead in, consisting of the first 6 patients to complete cycle 3. RESULTS A total of seven patients were enrolled to the safety lead-in: 2 women; 5 patients with astrocytoma, 2 oligodendroglioma. Patients had a median age of 45 (range 29-63) and median KPS 90 (range 80-100). Median number of recurrences was 3.5 (range 1-5). All had received prior alkylating therapy and all but 1 patient had received prior RT. No patients were taking steroids at the time of enrollment. Six patients completed the dose-limiting toxicity (DLT) period without any DLTs. One patient experienced clinical progression on pembrolizumab monotherapy prior to the start of combination therapy and was thus replaced. No grade 3 or 4 toxicities were seen through the DLT period. The most common clinical toxicities at least possibly related to treatment were grade 1 and 2 fatigue (n = 4), nausea (n = 3) and constipation (n = 2). Hematological toxicities include grade 1 anemia (n = 2) and decreased platelet count (n = 1). CONCLUSIONS The combination of olaparib, temozolomide, and pembrolizumab was well tolerated in this cohort. Following completion of the safety lead-in, the trial was redesigned to minimize the length of pembrolizumab monotherapy and introduce combination therapy in cycle 1. Enrollment is ongoing. NCT05188508.

PATH-62. RAMAN-BASED AI PLATFORM TO ACCELERATE THE DIAGNOSIS AND MANAGEMENT OF GLIOMAS VIA RAPID METHYLATION PROFILING

Abstract BACKGROUND DNA methylation profiling and subtyping of gliomas has become an integral part of the diagnosis and treatment of glioma patients but remains a challenge due to the sample preparation and time requirements of the existing methylation profiling technology. We hypothesized that machine learning and Raman spectroscopy, which creates fast molecular fingerprints of samples in situ based on chemical signatures rather than the use of exogenous dyes, can provide a fast alternative to the existing approaches for methylation profiling and classification of gliomas. METHODS Raman spectroscopy at the spatial resolution of less than 300nm was used for molecular fingerprinting of the regions of interest using 1mm2 Formalin-Fixed Paraffin-Embedded (FFPE) tissue spots from 45 patient samples with known LGm1 to LGm6 methylation subtypes. Spectral information (over 1738 frequencies) was used to construct tumor/non-tumor, IDH1WT/IDH1mut, and methylation-subtype classifiers. Oversampling was used to obtain subtype-balanced data distributions. Supervised wrapper methods and random forests were used to identify the top 20 most discriminatory Raman frequencies. Stimulated Raman spectroscopy was used to validate the findings. RESULTS We developed APOLLO - a novel platform based on spontaneous Raman spectroscopy and machine learning -- for predicting the DNA methylation subtypes of FFPE glioma tissue specimens. APOLLO discriminates tumors from non-tumor areas with 98% accuracy and discriminates IDH1mut versus IDH1WT tumors with 82% accuracy. APOLLO also achieved high discriminatory power between G-CIMP-high and G-CIMP-low molecular phenotypes (ROC of 0.75), subtypes of lower-grade IDH1mut gliomas with significantly different clinical outcomes. We determined that the Raman shifts important for discriminating IDH1mut versus IDH1wt tumors are associated with novel lipid-metabolism signatures of IDH1mut glioma. CONCLUSIONS The development of APOLLO allows fast, reliable, and accurate prediction of methylation subtypes of glioma which can speed diagnosis and, once validated on fresh tissue, can be implemented in the operating room.

SURG-41. PROGNOSTIC IMPACT OF EXTENDED RESECTIONS IN IDH MUTANT LOWER-GRADE DIFFUSE GLIOMA: RESULTS FROM A VOLUMETRIC ANALYSIS

Abstract In IDH mutant (IDHmut) glioma, the prognostic impact of extended resections is still under debate. A potential outcome benefit may be influenced by the tumor’s molecular phenotype. Also, many studies lack objective quantitative assessment of residual tumor volume (RTV). Here, we analyzed the prognostic benefit of surgery in a molecularly defined cohort of patients harboring an astrocytoma or oligodendroglioma, IDHmut, WHO grade 2 and 3, for whom volumetric analysis of RTV was possible. Patient-, tumor- and treatment-related factors including pre- and post-operative MR FLAIR tumor volumes were correlated with progression-free (PFS) and overall (OS) survival. Confounders of resectability were analyzed by multiple linear regression. 206 patients treated at our institution over one decade were identified retrospectively. Mean age was 40.37 years. 105 patients suffered from IDHmut astrocytoma and 101 patients from oligodendroglioma. Resection (n = 185 patients; 89.8%) as opposed to biopsy was associated with prolonged PFS and OS in astrocytoma (p = 0.007; p = 0.038) and WHO grade 2 tumors (p = 0.012; p < 0.0001). In patients undergoing resection, median pre- and post-operative tumor volumes did not differ between tumor subtypes but were significantly larger in WHO grade 3 than 2 tumors (pre-operative: 71.3 vs. 28.8 cm3; RTV: 7.78 vs. 1.98 cm3). Median RTV of the complete cohort was 4.6 cm3. There was a stepwise improvement of outcome with decreasing RTV (PFS: p = 0.0003; OS: p = 0.0004; data given for quartiles), with the strongest effect observed for patients with no RTV (median PFS: undefined vs. 58 months; p = 0.007). In multivariable analysis, RTV independently predicted OS (p = 0.001; HR 1.012) but not PFS. Resectability was only influenced by pre-operative FLAIR tumor volume (p < 0.0001). In summary, a continuous association of RTV and outcome was observed, even at the highest levels of resection. This finding was more pronounced in astrocytoma. Thus, a maximal resection should be strived for whenever safely achievable.

TMIC-36. SPATIAL ARCHITECTURE OF HIGH-GRADE GLIOMA REVEALS TUMOR HETEROGENEITY WITHIN DISTINCT DOMAINS

Abstract High-grade gliomas are aggressive primary brain cancers with poor response to standard regimens, driven by immense heterogeneity. In isocitrate dehydrogenase (IDH) wild-type high-grade glioma (glioblastoma, GBM), increased intra-tumoral heterogeneity is associated with more aggressive disease. Recently, spatial technologies have emerged to dissect this complex heterogeneity within the tumor ecosystem by preserving cellular organization in situ. Here, we construct a high-resolution molecular landscape of GBM and IDH-mutant high-grade glioma patient samples to investigate the cellular subtypes and spatial communities that compose high-grade glioma using digital spatial profiling and spatial molecular imaging. This uncovered striking diversity of the tumor and immune microenvironment, that is embodied by the heterogeneity of the inferred copy-number alterations in the tumor. Reconstructing the tumor architecture revealed two distinct niches, one composed of tumor cell states that most closely resemble normal glial cells, associated with microglia; and the other niche populated by monocytes and mesenchymal tumor cells. We further reveal that communication between tumor and immune cells is underpinned by tumor-specific ligands, such as TGFb signaling in astrocyte-like tumor cells. This primary study reveals high levels of intra-tumoral heterogeneity in high-grade gliomas, associated with a diverse immune landscape within spatially localized regions.

CTNI-46. UPFRONT VERSUS DEFERRED TREATMENT IN LOWER GRADE IDH-MUTANT GLIOMAS: A SINGLE-CENTER RETROSPECTIVE ANALYSIS

Abstract BACKGROUND IDH-mutant gliomas are a diverse group of gliomas possessing a mutation in the isocitrate dehydrogenase enzyme. The treatment for both oligodendroglioma (1p/19q co-deleted) and astrocytoma includes resection followed by radiation therapy and chemotherapy. However, there is debate over the optimal timing of adjuvant treatment after surgery. An initial observation approach is sometimes pursued, particularly after gross total resection in young adults. We sought to examine the impact of timing of treatment in order to inform clinical decision-making. METHODS We identified 286 biopsied or resected glial tumors treated at MD Anderson Cancer Center from July 2015 to June 2022. Tumors were categorized using available molecular data based on the WHO 2021 diagnostic criteria. Progression-free survival was analyzed using Kaplan-Meier estimates. RESULTS Of 286 tumors, 232 had identified IDH-mutation, of which 89 were 1p/19q co-deleted and 143 were non-co-deleted. Of oligodendroglioma patients, 71 received either upfront chemotherapy, radiation or both and 18 received treatment upon progression; of astrocytoma patients, 96 were treated upfront and 47 received treatment at progression. Among oligodendroglioma patients, there were no significant differences in PFS between treatment timing groups (75.6 vs 66.7 months, P = 0.18). There was additionally no difference between oligodendroglioma patients treated initially with PC or PCV regimens vs temozolomide (not reached vs 75.4 months, P = 0.24). Among astrocytoma patients, upfront treatment was associated with longer PFS (93.8 vs 45.2 months, P < 0.01). Patients with low-risk grade 2 gliomas (age <40 and gross total resection) also showed longer PFS with upfront treatment (138.0 vs 45.2 months, P = 0.03). CONCLUSION Overall, the results in this molecularly defined cohort suggest a progression-free survival benefit from upfront treatment in IDH-mutant lower grade gliomas, including in low-risk gliomas. The optimal timing and nature of adjuvant treatment for lower grade gliomas remains a matter of debate.

SURG-04. FAST DETECTION OF GLIOMA INFILTRATION USING LABEL-FREE OPTICAL MICROSCOPY AND DEEP NEURAL NETWORKS

Abstract INTRODUCTION Fast and accurate detection of tumor infiltration is a central challenge in the comprehensive management of diffuse glioma patients. Despite our best real-time tumor detection strategies, such as intraoperative MRI and fluorescence-guided surgery, dense and safely resectable tumor infiltration remains at the surgical margin in over 85% of diffuse glioma patients. Patterns of treatment failure demonstrate that glioma recurrence occurs at the surgical margin in the majority of patients due to residual tumor burden. Objective Here, we present FastGlioma, an artificial intelligence (AI)-based intraoperative diagnostic system for fast (< 10 seconds) detection of diffuse glioma infiltration at microscopic resolution without the need for tumor-specific markers. Method FastGlioma is trained using large-scale, self-supervised visual feature learning on stimulated Raman histology (SRH), a rapid, label-free, optical microscopy technique, and a GPT-style whole slide SRH tumor infiltration scoring method. We pushed the performance limits of FastGlioma by investigating the trade-off between imaging speed versus accuracy for microscopic tumor detection. RESULTS In a large prospective external testing cohort of diffuse glioma patients (180 patients, 935 surgical margin specimens) who underwent intraoperative SRH imaging, we demonstrate that FastGlioma was able to detect and quantify microscopic tumor infiltration with an average AUROC of 92.1 +/- 0.0%, performing on par with three expert neuropathologists on the same task. FastGlioma is over 10X faster than previous SRH-based methods and 100X faster than conventional H&E histology. Finally, we demonstrate that FastGlioma was > 20% more accurate at detecting dense tumor infiltration when compared to radiologic features or 5-aminolevulinic fluorescence (98.0% versus 77.8% accuracy) for both IDH-mutant diffuse gliomas and IDH-wildtype glioblastomas. CONCLUSION Our results demonstrate how intraoperative optical imaging and deep neural networks can achieve fast and accurate tumor detection, unlocking the role of AI in improving the surgical management of brain tumor patients.

CTNI-41. PHASE II AND PHASE 0 RESULTS OF ABTC 1801: A MULTI-ARM CLINICAL TRIAL OF THE PARP INHIBITOR PAMIPARIB WITH VERY LOW DOSE METRONOMIC TEMOZOLOMIDE IN RECURRENT IDH MUTANT GLIOMAS

Abstract BACKGROUND Preclinical studies have demonstrated that IDH1-mutant (IDHmt) gliomas harbor a BRCAness phenotype with a defect in homologous recombination that confers PARP inhibitor sensitivity. METHODS The phase II component of ABTC 1801 examined the efficacy of the combination of pamiparib (BeiGene BGB-290) with low dose metronomic temozolomide in recurrent IDHmt grade 2 and 3 gliomas. In this two-stage design, Arm A enrolled patients who had failed two lines and Arm B a single line of alkylator therapy. Pamiparib and temozolomide doses based on phase I results was 60 mg BID and 20 mg daily. Primary endpoint was objective response rate (ORR). RESULTS 39 patients (Arm A 15, Arm B 24) enrolled in the phase II. Median age was 45 (range: 25-69), 56% male, and median KPS 90. 72% of tumors were MGMT methylated. There were no confirmed responses in Arm A and one in Arm B; neither arm met the threshold for additional accrual. One-third of subjects discontinued treatment for reasons other than progressive disease. Estimated median PFS was 5.8 months in Arm A and 11.3 months in Arm B. Seven subjects (Arm A 3, Arm B 4) developed DLT during treatment. Grade 3+ toxicity was principally hematologic; 9 patients had grade 3 anemia, 7 grade 3 and 3 grade 4 neutropenia, and 3 grade 3 thrombocytopenia. In enhancing and non-enhancing tumors from 8 surgical arm patients, median unbound drug tumor/plasma ratios were 0.98 and 0.92, respectively; and median unbound pamiparib tumor concentrations were 209 and 188 nmol/L (or nmol/kg), respectively, which were >20-fold the in vitro IC50 for PARP inhibition. CONCLUSIONS While pamiparib appeared to achieve sufficient pharmacologically active concentrations in both enhancing and non-enhancing tumors, combination with temozolomide did not produce a meaningful ORR in IDHmt recurrent gliomas. Cumulative hematologic toxicity was substantial.

BIOM-09. OPPOSING EFFECTS OF LINKED CX3CR1 GERMLINE VARIANTS ON SURVIVAL AND IMMUNE ACTIVATION IN GLIOMA

Abstract Linkage-disequilibrium connects CX3CR1 V249I and T280M single-nucleotide polymorphisms; V249I occurs as a single-variant (SV) and T280M exclusively as a double-variant (DV) concurrent with V249I. In low-grade gliomas (LGG), we found improved median overall-survival (mOS) in SV (n = 14, mOS 21.03yrs), compared to WT (n = 45, mOS 9.41yrs) and DV (n = 31, mOS 10.49yrs; p = 0.037 Log-rank). In TCGA glioblastoma (GBM), SV (n = 69, mOS 15.65mo) improved survival over DV (n = 106, mOS 11.74mo; p = 0.044 Log-rank). In a separate GBM cohort, bulk RNA-sequencing revealed MMP9 over-expression in DV (n = 15) compared to SV (n = 10; log2FC 2.87, p-adj 0.079). On a single-gene basis, MMP9 expression was decreased in SV compared to DV and WT (n = 33; p = 0.044, Kruskal-Wallis). MMP9 promotes tumor angiogenesis and invasion. SV showed SPP1 over-expression compared to DV (log2FC -1.75, p-adj 0.026), with decreased SPP1 expression in both WT and DV compared to SV (p = 0.004, Kruskal-Wallis). SPP1 is a pro-inflammatory cytokine enriched in glioma-associated macrophages. Gene Ontology revealed enrichment of biological processes: neutrophil migration, granulocyte chemotaxis, and neutrophil chemotaxis in SV (p< 0.05). We single-cell RNA-sequenced IDH mutant gliomas (51777 cells). We subset and re-clustered myeloid-derived cells (microglia/macrophages, 8944 cells), identifying thirteen clusters. Myeloid-derived cells clustered by CX3CR1 status, with 50.8% of SV cells in cluster five and 85.3% of DV cells in clusters six or seven. Cluster five over-expressed IL1B (average-log2FC 3.23), a tumor-suppressive M1 macrophage marker. Clusters six and seven were characterized by IFIT genes – immunomodulatory in myeloid-derived cells (IFIT3 average-log2FC 2.65 and 2.06). Assessing CX3CR1 status in normal population – 74.2% are WT, 10.0% SV, and 15.7% DV. In glioma patients, we identify 59.9% WT, 14.9% SV, and 25.2% DV – an increase of 49% in SV and 61% in DV (p = 1.95e-6, Chi-square). Our findings demonstrate opposing effects of linked CX3CR1 germline variants on glioma survival and indicate enhanced immune activation in SV.

CTNI-47. DOSE ESCALATION OF ASTX727 IN ADULT PATIENTS WITH RECURRENT/PROGRESSIVE NON-ENHANCING IDH MUTANT GLIOMAS

Abstract BACKGROUND IDH mutant gliomas typically display a hypermethylation pattern known as the glioma CpG island methylator phenotype (G-CIMP) which results in gene activation that promotes gliomagenesis. This study aims to reverse this methylation signature and disrupt tumor growth via treatment with an oral demethylating agent. METHODS This is 2-stage clinical trial investigating oral ASTX727 (decitabine + cedazuridine, a cytidine deaminase inhibitor, as a combination tablet) in patients with recurrent primarily non-enhancing IDH mutant gliomas. The Dose Escalation Stage consisted of a single arm 3 + 3 design. The primary objective was to establish the MTD and assess safety in this patient population. RESULTS Eleven pts (F = 45%, M = 55%) with a median age of 44 yrs (range 26-61 yrs) were enrolled. Two DLTs (grade 4 neutropenia for >72 hrs) were observed in 5 pts enrolled at the starting dose (35 mg decitabine/ 100 mg cedazuridine for 5 consecutive days). Six additional patients were enrolled at dose level -1 (35 mg decitabine/100 mg cedazuridine for 4 consecutive days). There were no DLTs at dose level -1 and this was declared the MTD. Grade ≥ 3 AEs included neutropenia (5 pts), leukopenia (1 pt), lymphopenia (1 pt), hyponatremia (1 pt) and increased ALT (1 pt). Best treatment response was SD in 11 patients. At the time of last follow-up (5/15/23) 10 pts have discontinued treatment (8 for PD, and 2 based on physician decision), 2 pts (18%) have died due to disease progression, 8 pts remain alive and in follow-up, and 1 patient remains on treatment. Median duration on treatment was 212 days (range 36 days – not reached). CONCLUSIONS ASTX727 was well tolerated in patients with recurrent non-enhancing IDH mutant glioma at dose level -1 with no DLTs . A surgical expansion cohort is currently enrolling to confirm drug target engagement and explore pharmacodynamics.

Differential metabolic alterations in IDH1 mutant vs. wildtype glioma cells promote epileptogenesis through distinctive mechanisms.

Glioma-related epilepsy (GRE) is a hallmark clinical presentation of gliomas with significant impacts on patient quality of life. The current standard of care for seizure management is comprised of anti-seizure medications (ASMs) and surgical resection. Seizures in glioma patients are often drug-resistant and can often recur after surgery despite total tumor resection. Therefore, current research is focused on the pro-epileptic pathological changes occurring in tumor cells and the peritumoral environment. One important contribution to seizures in GRE patients is metabolic reprogramming in tumor and surrounding cells. This is most evident by the significantly heightened seizure rate in patients with isocitrate dehydrogenase mutated (IDHmut) tumors compared to patients with IDH wildtype (IDHwt) gliomas. To gain further insight into glioma metabolism in epileptogenesis, this review compares the metabolic changes inherent to IDHmut vs. IDHwt tumors and describes the pro-epileptic effects these changes have on both the tumor cells and the peritumoral environment. Understanding alterations in glioma metabolism can help to uncover novel therapeutic interventions for seizure management in GRE patients.

Tumor Volume Growth Rates and Doubling Times during Active Surveillance of IDH-mutant Low-Grade Glioma.

Isocitrate dehydrogenase-mutant (IDH-mt) gliomas are incurable primary brain tumors characterized by a slow-growing phase over several years followed by a rapid-growing malignant phase. We hypothesized that tumor volume growth rate (TVGR) on MRI may act as an earlier measure of clinical benefit during the active surveillance period. We integrated three-dimensional volumetric measurements with clinical, radiologic, and molecular data in a retrospective cohort of IDH-mt gliomas that were observed after surgical resection in order to understand tumor growth kinetics and the impact of molecular genetics. Using log-linear mixed modeling, the entire cohort (n = 128) had a continuous %TVGR per 6 months of 10.46% [95% confidence interval (CI), 9.11%-11.83%] and a doubling time of 3.5 years (95% CI, 3.10-3.98). High molecular grade IDH-mt gliomas, defined by the presence of homozygous deletion of CDKN2A/B, had %TVGR per 6 months of 19.17% (95% CI, 15.57%-22.89%) which was significantly different from low molecular grade IDH-mt gliomas with a growth rate per 6 months of 9.54% (95% CI, 7.32%-11.80%; P < 0.0001). Using joint modeling to comodel the longitudinal course of TVGR and overall survival, we found each one natural logarithm tumor volume increase resulted in more than a 3-fold increase in risk of death (HR = 3.83; 95% CI, 2.32-6.30; P < 0.0001). TVGR may be used as an earlier measure of clinical benefit and correlates well with the WHO 2021 molecular classification of gliomas and survival. Incorporation of TVGR as a surrogate endpoint into future prospective studies of IDH-mt gliomas may accelerate drug development.

CircIQGAP1 regulates RCAN1 and RCAN2 through the mechanism of ceRNA and promotes the growth of malignant glioma

Circular RNA (circRNA) is one of non-coding RNA with specific circular structure, which has been found to be involved in regulating a series of malignant biological behaviors in many malignant tumors. In this study, based on the IDH1 molecular typing of gliomas, we identified a significant downregulation of circRNA (circIQGAP1) expression in IDH1 mutant gliomas by high-throughput sequencing. In 79 tissue samples, we confirmed that circIQGAP1 expression was significantly downregulated in IDH1 mutant gliomas, and that low circIQGAP1 expression was positively associated with better prognosis. Knockdown of circIQGAP1 in glioma cell lines inhibited glioma cell malignancy and conversely overexpression of circIQGAP1 promoted glioma malignancy. circIQGAP1 regulated glioma cell migration, proliferation, invasion and apoptosis through miR-1256/RCAN1/Bax/Bcl-2/Caspase3 and miR-622/RCAN2/Bax/Bcl-2/Caspase3 axes. These results suggest that circIQGAP1 plays an important role in glioma development, promotes tumor growth, and is a potential therapeutic target for glioma.

83. Cytogenetic and molecular characterization of IDH-mutant adult-type diffuse gliomas with near-total 1p/19q co-deletions

83. Cytogenetic and molecular characterization of IDH-mutant adult-type diffuse gliomas with near-total 1p/19q co-deletions

Radiogenomics Provides Insights into Gliomas Demonstrating Single-Arm 1p or 19q Deletion.

IDH-mutant gliomas are further divided on the basis of 1p/19q status: oligodendroglioma, IDH-mutant and 1p/19q-codeleted, and astrocytoma, IDH-mutant (without codeletion). Occasionally, testing may reveal single-arm 1p or 19q deletion (unideletion), which remains within the diagnosis of astrocytoma. Molecular assessment has some limitations, however, raising the possibility that some unideleted tumors could actually be codeleted. This study assessed whether unideleted tumors had MR imaging features and survival more consistent with astrocytomas or oligodendrogliomas. One hundred twenty-one IDH-mutant grade 2-3 gliomas with 1p/19q results were identified. Two neuroradiologists assessed the T2-FLAIR mismatch sign and calcifications, as differentiators of astrocytomas and oligodendrogliomas. MR imaging features and survival were compared among the unideleted tumors, codeleted tumors, and those without 1p or 19q deletion. The cohort comprised 65 tumors without 1p or 19q deletion, 12 unideleted tumors, and 44 codeleted. The proportion of unideleted tumors demonstrating the T2-FLAIR mismatch sign (33%) was similar to that in tumors without deletion (49%; P = .39), but significantly higher than codeleted tumors (0%; P = .001). Calcifications were less frequent in unideleted tumors (0%) than in codeleted tumors (25%), but this difference did not reach statistical significance (P = .097). The median survival of patients with unideleted tumors was 7.8 years, which was similar to that in tumors without deletion (8.5 years; P = .72) but significantly shorter than that in codeleted tumors (not reaching median survival after 12 years; P = .013). IDH-mutant gliomas with single-arm 1p or 19q deletion have MR imaging appearance and survival that are similar to those of astrocytomas without 1p or 19q deletion and significantly different from those of 1p/19q-codeleted oligodendrogliomas.

Simultaneous quantification of perfusion, permeability, and leakage effects in brain gliomas using dynamic spin-and-gradient-echo echoplanar imaging MRI

ObjectiveTo determine the feasibility and biologic correlations of dynamic susceptibility contrast (DSC), dynamic contrast enhanced (DCE), and quantitative maps derived from contrast leakage effects obtained simultaneously in gliomas using dynamic spin-and-gradient-echo echoplanar imaging (dynamic SAGE-EPI) during a single contrast injection.Materials and methodsThirty-eight patients with enhancing brain gliomas were prospectively imaged with dynamic SAGE-EPI, which was processed to compute traditional DSC metrics (normalized relative cerebral blood flow [nrCBV], percentage of signal recovery [PSR]), DCE metrics (volume transfer constant [Ktrans], extravascular compartment [ve]), and leakage effect metrics: ΔR2,ss* (reflecting T2*-leakage effects), ΔR1,ss (reflecting T1-leakage effects), and the transverse relaxivity at tracer equilibrium (TRATE, reflecting the balance between ΔR2,ss* and ΔR1,ss). These metrics were compared between patient subgroups (treatment-naïve [TN] vs recurrent [R]) and biological features (IDH status, Ki67 expression).ResultsIn IDH wild-type gliomas (IDHwt—i.e., glioblastomas), previous exposure to treatment determined lower TRATE (p = 0.002), as well as higher PSR (p = 0.006), Ktrans (p = 0.17), ΔR1,ss (p = 0.035), ve (p = 0.006), and ADC (p = 0.016). In IDH-mutant gliomas (IDHm), previous treatment determined higher Ktrans and ΔR1,ss (p = 0.026). In TN-gliomas, dynamic SAGE-EPI metrics tended to be influenced by IDH status (p ranging 0.09–0.14). TRATE values above 142 mM−1s−1 were exclusively seen in TN-IDHwt, and, in TN-gliomas, this cutoff had 89% sensitivity and 80% specificity as a predictor of Ki67 > 10%.ConclusionsDynamic SAGE-EPI enables simultaneous quantification of brain tumor perfusion and permeability, as well as mapping of novel metrics related to cytoarchitecture (TRATE) and blood–brain barrier disruption (ΔR1,ss), with a single contrast injection.Clinical relevance statementSimultaneous DSC and DCE analysis with dynamic SAGE-EPI reduces scanning time and contrast dose, respectively alleviating concerns about imaging protocol length and gadolinium adverse effects and accumulation, while providing novel leakage effect metrics reflecting blood–brain barrier disruption and tumor tissue cytoarchitecture.Key Points• Traditionally, perfusion and permeability imaging for brain tumors requires two separate contrast injections and acquisitions.• Dynamic spin-and-gradient-echo echoplanar imaging enables simultaneous perfusion and permeability imaging.• Dynamic spin-and-gradient-echo echoplanar imaging provides new image contrasts reflecting blood–brain barrier disruption and cytoarchitecture characteristics.Graphical

Tumor heterogeneity and tumor-microglia interactions in primary and recurrent IDH1-mutant gliomas

The isocitrate dehydrogenase (IDH) gene is recurrently mutated in adult diffuse gliomas. IDH-mutant gliomas are categorized into oligodendrogliomas and astrocytomas, each with unique pathological features. Here, we use single-nucleus RNA and ATAC sequencing to compare the molecular heterogeneity of these glioma subtypes. In addition to astrocyte-like, oligodendrocyte progenitor-like, and cycling tumor subpopulations, a tumor population enriched for ribosomal genes and translation elongation factors is primarily present in oligodendrogliomas. Longitudinal analysis of astrocytomas indicates that the proportion of tumor subpopulations remains stable in recurrent tumors. Analysis of tumor-associated microglia/macrophages (TAMs) reveals significant differences between oligodendrogliomas, with astrocytomas harboring inflammatory TAMs expressing phosphorylated STAT1, as confirmed by immunohistochemistry. Furthermore, inferred receptor-ligand interactions between tumor subpopulations and TAMs may contribute to TAM state diversity. Overall, our study sheds light on distinct tumor populations, TAM heterogeneity, TAM-tumor interactions in IDH-mutant glioma subtypes, and the relative stability of tumor subpopulations in recurrent astrocytomas.