IDH-mutant Lower-grade Gliomas Research Articles

Association of Clinical, Tumor, and Treatment Characteristics With Seizure Control in Patients With IDH1/2-Mutant Lower-Grade Glioma.

Patients with IDH1/2-mutant lower-grade glioma have a high frequency of seizures. We aimed to investigate the correlations between seizures and tumor/patient characteristics and the impact of surgery and adjuvant treatments (AT) on seizure control along the disease trajectory. We retrospectively included patients with IDH1/2-mutant lower-grade glioma who underwent surgery at the neurosurgery divisions of the University of Turin and Milan and were treated at the Division of Neuro-Oncology of Turin. Inclusion criteria were a diagnosis according to the 2021 WHO Classification and presentation with seizures; exclusion criteria were presence of CDKN2A/B homozygous deletion, intense/ring contrast enhancement on MRI at presentation, and small tissue biopsy. We evaluated seizure freedom for 2 months after surgery, 6 months from starting observation or AT, at recurrence, and for 6 months after treatments of recurrence. We included 150 patients. There were 77 (51%) and 31 (21%) patients with IDH-mutant/1p19q-codeleted grade 2 and 3 oligodendroglioma and 30 (20%) and 12 (8%) with IDH-mutant grade 2 and 3 astrocytoma, respectively. Total resection was accomplished in 68 (45%). Seventy-five patients (50%) received AT while the remaining 75 were observed with MRI. After 6 months after AT, 28 of 29 patients (96.5%) displayed seizure reduction, 5 of 28 (18%) being seizure-free. 66 of 124 patients (53%) had seizures at recurrence. After 6 months after second-line treatments, 60 of 66 patients (91%) had seizure reduction, 11 (17%) being seizure-free. In multivariable analyses, grade 3 histology positively correlated with seizure freedom at 2 months after surgery (OR 3.5, 1.4-8.9, p = 0.008), 6 months after AT (OR 9.0, 1.5-54.9, p = 0.017), and 6 months after treatment of recurrence (OR 4.9, 1.5-16.5, p = 0.009). Adjuvant radiotherapy reduced seizures at recurrence in a univariate analysis (OR 0.14, 0.03-0.7, p = 0.020). Patients with seizure freedom after surgery and AT displayed longer progression-free survival (PFS) (65, 24.5-105, vs 48 months, 32-63.5, p = 0.037). This study analyzed seizure control in patients with IDH1/2-mutant lower-grade glioma across multiple time points. Grade 3 correlated with better seizure control throughout the entire disease trajectory, and seizure freedom after surgery and AT correlated with a longer PFS regardless of tumor grade. These results could serve as an external control arm in clinical trials evaluating the efficacy on seizures of antitumor agents in patients with IDH-mutant lower-grade glioma.

Low- and high-grade glioma-associated vascular cells differentially regulate tumor growth.

A key feature distinguishing high-grade glioma (HG) from low-grade glioma (LG) is the extensive neovascularization and endothelial hyperproliferation. Prior work has shown that tumor-associated vasculature from HG is molecularly and functionally distinct from normal brain vasculature and expresses higher levels of pro-tumorigenic factors that promote glioma growth and progression. However, it remains unclear whether vessels from LG also express pro-tumorigenic factors, and to what extent they functionally contribute to glioma growth. Here, we profile the transcriptomes of glioma-associated vascular cells (GVC) from IDH-mutant (mIDH) LG and IDH-wildtype (wIDH) HG and show that they exhibit significant molecular and functional differences. LG-GVC show enrichment of extracellular matrix-related gene sets and sensitivity to anti-angiogenic drugs, whereas HG-GVC display an increase in immune response-related gene sets and anti-angiogenic resistance. Strikingly, conditioned media from LG-GVC inhibits the growth of wIDH glioblastoma cells, whereas HG-GVC promotes growth. In vivo co-transplantation of LG-GVC with tumor cells reduces growth, whereas HG-GVC enhances tumor growth in orthotopic xenografts. We identify ASPORIN (ASPN), a small leucine-rich repeat proteoglycan, highly enriched in LG-GVC as a growth suppressor of wIDH glioblastoma cells in vitro and in vivo. Together, these findings indicate that GVC from LG and HG are molecularly and functionally distinct and differentially regulate tumor growth. Implications: This study demonstrated that vascular cells from IDH-mutant LG and IDH-wildtype HG exhibit distinct molecular signatures and have differential effects on tumor growth via regulation of ASPN-TGFβ1-GPM6A signaling.

10109-COT-13 LONG-TERM FOLLOW-UP OF FLAIR HIGH LESION IN THE BRAIN

Abstract AIM Incidental FLAIR (Fluid Attenuated Inversion Recovery) high-intensity lesion in the brain can be considered as IDH-mutant low-grade glioma (LGG). Differential diagnosis includes trauma, ischemic changes, demyelinating diseases, and other inflammatory diseases. The biopsy is sometimes high risk for a young patient or an asymptomatic patient with a lesion in the brain stem, motor or language area. Imaging intervals vary among hospitals and the method for regular follow-up for these cases has not been established. METHODS We have studied 26 patients with FLAIR high lesion from 2012 to 2022. In cases of suspected LGG, the biopsy was performed, when necessary, after consultation with the patient and family. Our neurosurgery team protocol was to perform PET-MRI at the first consultation, and if there was negative, we have scheduled MRI examination at the next visit in one month. Then, MRI was performed every 2-3 months for the first year and every 3-6 months thereafter. The clinical features of these FLAIR high lesion and their differentiations from LGG in our cases are examined. RESULTS Biopsy was performed in 5 cases, but no tumor was found. The male-to-female ratio was 7:19, which was more common in female. The median age at onset was 44 years (15-47 years), showing a bimodal distribution with peaks in younger and older individuals. Among 26 cases, 14 cases had been unchanged for more than 5 years. The median maximum lesion diameter was 17 mm (8-47 mm). An annual average increase of LGG has been reported to be 3-5 mm in (Pallud, 2010). There were no cases diagnosed as glioma in cases where no expansion was seen after 5 years or more. CONCLUSION In this study, the possibility of glioma was considered to be low for cases in which no expansion on MRI was seen after 5 years or more.

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.

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.

Oligodendrogliomas tend to infiltrate the frontal aslant tract, whereas astrocytomas tend to displace it

IntroductionMR-tractography is increasingly used in neurosurgical practice to evaluate the anatomical relationships between glioma and nearby subcortical tracts. In some patients, the subcortical tracts seem displaced by the glioma, while in other patients, the subcortical tracts seem infiltrated without displacement. At this point, it is unknown whether these different patterns are related to tumor type. The aim of this exploratory study was to investigate whether tumor type is related to the spatial tractography pattern of the frontal aslant tract (FAT) in low-grade gliomas (LGGs).MethodsIn 64 IDH-mutated LGG patients, the FAT was generated using a pipeline for automatic tractography. In 41 patients, the glioma adjoined the FAT, and four blinded reviewers independently assessed the following two dichotomous categories (yes/no): (i) glioma displaces the tract, and (ii) glioma infiltrates the tract.ResultsFisher’s exact tests demonstrated strong and significant positive associations between displacement and astrocytomas (p = .002, φ = .497) and infiltration and oligodendrogliomas (p = .004, φ = .484). The interobserver agreement was good for both categories: (i) κ = 0.76 and (ii) κ = 0.71.ConclusionHigh sensitivity but low specificity for displacement in astrocytomas demonstrates that in the case of an astrocytoma, the tract is most likely displaced, but that displacement in itself is not necessarily predictive for astrocytomas, as oligodendrogliomas may both infiltrate and displace a tract. Overall, these results demonstrate that oligodendrogliomas tend to infiltrate the nearby subcortical tract, whereas astrocytomas only tend to displace it.

Presurgical Executive Functioning in Low-Grade Glioma Patients Cannot Be Topographically Mapped.

Executive dysfunctions have a high prevalence in low-grade glioma patients and may be the result of structural disconnections of particular subcortical tracts and/or networks. However, little research has focused on preoperative low-grade glioma patients. The frontotemporoparietal network has been closely linked to executive functions and is substantiated by the superior longitudinal fasciculus. The aim of this study was to investigate their role in executive functions in low-grade glioma patients. Patients from two neurological centers were included with IDH-mutated low-grade gliomas. The sets of preoperative predictors were (i) distance between the tumor and superior longitudinal fasciculus, (ii) structural integrity of the superior longitudinal fasciculus, (iii) overlap between tumor and cortical networks, and (iv) white matter disconnection of the same networks. Linear regression and random forest analyses were performed. The group of 156 patients demonstrated significantly lower performance than normative samples and had a higher prevalence of executive impairments. However, both regression and random forest analyses did not demonstrate significant results, meaning that neither structural, cortical network overlap, nor network disconnection predictors explained executive performance. Overall, our null results indicate that there is no straightforward topographical explanation of executive performance in low-grade glioma patients. We extensively discuss possible explanations, including plasticity-induced network-level equipotentiality. Finally, we stress the need for the development of novel methods to unveil the complex and interacting mechanisms that cause executive deficits in low-grade glioma patients.

Subventricular Zone Involvement in IDH Mutant Lower-Grade Glioma: Impact on Treatment and Patient Outcome

Subventricular Zone Involvement in IDH Mutant Lower-Grade Glioma: Impact on Treatment and Patient Outcome

Radiotherapy delays malignant transformation and prolongs survival in patients with IDH-mutant gliomas.

IDH-mutant lower-grade gliomas (LGGs, grade 2 or 3) eventually transform into secondary grade 4 astrocytomas (sA_IDHmut/G4). Here, we sought to describe the transformation time, risk factors, and outcomes in malignant transformation of IDH-mutant LGGs. We screened data for 108 patients with sA_IDHmut/G4 in the Chinese Glioma Genome Atlas who had initial IDH-mutant LGGs and underwent reoperation during 2005-2021. We evaluated the transformation time from IDH-mutant LGGs to sA_IDHmut/G4, and associated risk factors and outcomes. Malignant transformation was defined as pathological confirmation of grade 4 astrocytoma. The median age of the 108 patients with IDH-mutant LGGs was 35 years (range, 19-54); the median age at transformation was 40 years (range, 25-62); and the median follow-up time for all patients was 146 months (range, 121-171). The average transformation time was 58.8 months for all patients with LGGs (range, 5.9-208.1); 63.5 and 51.9 months for grade 2 and 3 gliomas, respectively; and 58.4 and 78.1 months for IDH-mutant/1p/19q-non-codeleted astrocytomas and IDH-mutant/1p/19q-codeleted oligodendrogliomas, respectively. Univariate and multivariate analysis indicated that radiotherapy [hazard ratio (HR), 0.29; 95% confidence interval (CI), 0.137-0.595; <i>P</i> = 0.001] and non-A blood type (HR, 0.37; 95% CI, 0.203-0.680; <i>P</i> = 0.001) were protective factors against delayed malignant transformation. Radiotherapy was associated with improved survival after transformation (HR, 0.44; 95% CI, 0.241-0.803; <i>P</i> = 0.008), overall survival (HR, 0.50; 95% CI, 0.265-0.972; <i>P</i> = 0.041), and progression-free survival (HR, 0.25; 95% CI, 0.133-0.479; <i>P</i> &lt; 0.0001) in patients with IDH-mutant gliomas. Radiotherapy is associated with delayed malignant transformation and improved survival in patients with IDH-mutant gliomas.

Is intracranial volume a risk factor for IDH-mutant low-grade glioma? A case–control study

PurposeRisk of cancer has been associated with body or organ size in several studies. We sought to investigate the relationship between intracranial volume (ICV) (as a proxy for lifetime maximum brain size) and risk of IDH-mutant low-grade glioma.MethodsIn a multicenter case–control study based on population-based data, we included 154 patients with IDH-mutant WHO grade 2 glioma and 995 healthy controls. ICV in both groups was calculated from 3D MRI brain scans using an automated reverse brain mask method, and then compared using a binomial logistic regression model.ResultsWe found a non-linear association between ICV and risk of glioma with increasing risk above and below a threshold of 1394 ml (p < 0.001). After adjusting for ICV, sex was not a risk factor for glioma.ConclusionIntracranial volume may be a risk factor for IDH-mutant low-grade glioma, but the relationship seems to be non-linear with increased risk both above and below a threshold in intracranial volume.

Multicenter clinical radiomics-integrated model based on [18F]FDG PET and multi-modal MRI predict ATRX mutation status in IDH-mutant lower-grade gliomas.

To develop a clinical radiomics-integrated model based on 18 F-fluorodeoxyglucose positron emission tomography ([18F]FDG PET) and multi-modal MRI for predicting alpha thalassemia/mental retardation X-linked (ATRX) mutation status of IDH-mutant lower-grade gliomas (LGGs). One hundred and two patients (47 ATRX mutant-type, 55 ATRX wild-type) diagnosed with IDH-mutant LGGs (CNS WHO grades 1 and 2) were retrospectively enrolled. A total of 5540 radiomics features were extracted from structural MR (sMR) images (contrast-enhanced T1-weighted imaging, CE-T1WI; T2-weighted imaging, and T2WI), functional MR (fMR) images (apparent diffusion coefficient, ADC; cerebral blood volume, CBV), and metabolic PET images ([18F]FDG PET). The random forest algorithm was used to establish a clinical radiomics-integrated model, integrating the optimal multi-modal radiomics model with three clinical parameters. The predictive effectiveness of the models was evaluated by receiver operating characteristic (ROC) and decision curve analysis (DCA). The optimal multi-modal model incorporated sMR (CE-T1WI), fMR (ADC), and metabolic ([18F]FDG) images ([18F]FDG PET+ADC+ CE-T1WI) with the area under curves (AUCs) in the training and test groups of 0.971 and 0.962, respectively. The clinical radiomics-integrated model, incorporating [18F]FDG PET+ADC+CE-T1WI, three clinical parameters (KPS, SFSD, and ATGR), showed the best predictive effectiveness in the training and test groups (0.987 and 0.975, respectively). The clinical radiomics-integrated model with metabolic, structural, and functional information based on [18F]FDG PET and multi-modal MRI achieved promising performance for predicting the ATRX mutation status of IDH-mutant LGGs. • The clinical radiomics-integrated model based on [18F]FDG PET and multi-modal MRI achieved promising performance for predicting ATRX mutation status in LGGs. • The study investigated the value of multicenter clinical radiomics-integrated model based on [18F]FDG PET and multi-modal MRI in LGGs regarding ATRX mutation status prediction. • The integrated model provided structural, functional, and metabolic information simultaneously and demonstrated with satisfactory calibration and discrimination in the training and test groups (0.987 and 0.975, respectively).

Spectroscopic imaging of D-2-hydroxyglutarate and other metabolites in pre-surgical patients with IDH-mutant lower-grade gliomas

PurposePrognostically favorable IDH-mutant gliomas are known to produce oncometabolite D-2-hydroxyglutarate (2HG). In this study, we investigated metabolite-based features of patients with grade 2 and 3 glioma using 2HG-specific in vivo MR spectroscopy, to determine their relationship with image-guided tissue pathology and predictive role in progression-free survival (PFS).MethodsForty-five patients received pre-operative MRIs that included 3-D spectroscopy optimized for 2HG detection. Spectral data were reconstructed and quantified to compare metabolite levels according to molecular pathology (IDH1R132H, 1p/19q, and p53); glioma grade; histological subtype; and T2 lesion versus normal-appearing white matter (NAWM) ROIs. Levels of 2HG were correlated with other metabolites and pathological parameters (cellularity, MIB-1) from image-guided tissue samples using Pearson’s correlation test. Metabolites predictive of PFS were evaluated with Cox proportional hazards models.ResultsQuantifiable levels of 2HG in 39/42 (93%) IDH+ and 1/3 (33%) IDH– patients indicated a 91.1% apparent detection accuracy. Myo-inositol/total choline (tCho) showed reduced values in astrocytic (1p/19q-wildtype), p53-mutant, and grade 3 (vs. 2) IDH-mutant gliomas (p < 0.05), all of which exhibited higher proportions of astrocytomas. Compared to NAWM, T2 lesions displayed elevated 2HG+ γ-aminobutyric acid (GABA)/total creatine (tCr) (p < 0.001); reduced glutamate/tCr (p < 0.001); increased myo-inositol/tCr (p < 0.001); and higher tCho/tCr (p < 0.001). Levels of 2HG at sampled tissue locations were significantly associated with tCho (R = 0.62; p = 0.002), total NAA (R = − 0.61; p = 0.002) and cellularity (R = 0.37; p = 0.04) but not MIB-1. Increasing levels of 2HG/tCr (p = 0.0007, HR 5.594) and thresholding (≥ 0.905, median value; p = 0.02) predicted adverse PFS.ConclusionIn vivo 2HG detection can reasonably be achieved on clinical scanners and increased levels may signal adverse PFS.

PET With 11C-Methyl-l-Methionine as a Predictor of Consequential Outcomes at the Time of Discontinuing Temozolomide-Adjuvant Chemotherapy in Patients With Residual IDH-Mutant Lower-Grade Glioma.

PurposeThe aim of this study was to clarify whether PET with 11C-methyl-l-methionine (11C-met PET) can predict consequential outcomes at the time of discontinuing temozolomide (TMZ)-adjuvant chemotherapy in patients with residual isocitrate dehydrogenase gene (IDH)–mutant lower-grade glioma.Patients and MethodsAmong 30 patients showing residual lesions of IDH-mutant lower-grade glioma, we compared the tumor-to-normal brain tissue ratio of standardized uptake values (SUVT/N) from 11C-met PET at the time of discontinuing TMZ-adjuvant chemotherapy with putative predictive factors including age, Karnofsky Performance Scale, number of courses of adjuvant therapy, residual tumor size, and promotor methylation status of O6-methylguanine-DNA methyl-transferase gene (MGMT). For each factor, progression-free survival (PFS) was compared between groups divided by cutoff values, determined to predict tumor relapse using receiver operating characteristic curves for each factor. Univariate and multivariate analyses were conducted using log-rank testing and Cox regression analysis, respectively. In addition, PFS was compared between patients grouped by combined findings from multiple predictors identified from univariate and multivariate analyses.ResultsUnivariate and multivariate analyses identified SUVT/N from 11C-met PET and MGMT methylation status as independent predictors of outcomes after TMZ discontinuation. When comparing 3 groups assigned by the combination of MGMT and SUVT/N findings, PFS differed significantly among groups.ConclusionsThe present study suggested that 11C-met PET at the time of discontinuing TMZ-adjuvant chemotherapy allows prediction of outcomes at least comparable to MGMT methylation status in patients with residual IDH-mutant lower-grade glioma. Further, 11C-met PET allows more precise prediction of outcomes by assessment in combination with MGMT findings.

Gyriform infiltration as imaging biomarker for molecular glioblastomas.

Molecular glioblastomas (i.e. without the histological but with the molecular characteristics of IDH-wild-type glioblastoma) frequently lack contrast enhancement, which can wrongly lead to suspect a lower-grade glioma. Herein, we aimed to assess the diagnostic value of gyriform infiltration as an imaging marker for molecular glioblastomas. Two independent investigators reviewed the MRI scans from patients with newly diagnosed gliomas for the presence of a gyriform infiltration defined as an elective cortical hypersignal on MRI FLAIR sequence. Diagnostic test performance of this sign for the diagnosis of molecular glioblastoma were calculated. A total of 426 patients were included, corresponding to 31 molecular glioblastoma, 294 IDH-wild-type glioblastoma, 50 IDH-mutant astrocytoma, and 51 IDH-mutant 1p19q-codeleted oligodendroglioma. A gyriform infiltration was observed in 16/31 (52%) molecular glioblastoma, 40/294 (14%) IDH-wild-type glioblastoma, and none of the IDH-mutant glioma. All the 56 gyriform-infiltration-positive tumors were IDH-wild-type and all but two had a TERT promoter mutation. The inter-rater agreement was good (κ = 0.69, p < 0.001). The sensitivity, specificity, positive predictive value and negative predictive value of the presence of a gyriform infiltration for the diagnosis of molecular glioblastoma were 52%, 90%, 29%, 96%, respectively. The median overall survival was better for gyriform-infiltration-negative patients compared to gyriform-infiltration-positive patients in the whole series and in patients with non-enhancing lesions (n = 95) (25.6 vs 16.9months, p = 0.005 and 20.2months vs not reached, p < 0.001). Gyriform infiltration is a specific imaging marker of molecular glioblastomas that can help distinguishing these tumors from IDH-mutant lower-grade gliomas.

Radiogenomic association between the T2-FLAIR mismatch sign and IDH mutation status in adult patients with lower-grade gliomas: an updated systematic review and meta-analysis.

To reveal a radiogenomic correlation between the presence of the T2-fluid-attenuated inversion recovery resection (T2-FLAIR) mismatch sign on MR images and isocitrate dehydrogenase (IDH) mutation status in adult patients with lower-grade gliomas (LGGs). A web-based systemic search for eligible literature up to April 13, 2021, was conducted on PubMed, Embase, and the Cochrane Library databases by two independent reviewers. This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. We included studies evaluating the accuracy of the T2-FLAIR mismatch sign in diagnosing the IDH mutation in adult patients with LGGs. The T2-FLAIR mismatch sign was defined as a T2-hyperintense lesion that is hypointense on FLAIR except for a hyperintense rim. Fourteen studies (n = 1986) were finally identified. The mean age of patients in the included studies ranged from 38.5 to 56 years. The pooled area under the curve (AUC), sensitivity, and specificity were obtained for each molecular profile: IDHmut-Codel: 0.46 (95% confidence interval [CI]: 0.42-0.50), 1% (95%CI: 0-7%), and 69% (95%CI: 62-75%), respectively; IDHmut-Noncodel: 0.75 (95%CI: 0.71-0.79), 42% (95%CI: 34-50%), and 99% (95%CI: 96-100%), respectively; IDH-Mutation regardless of 1p/19q codeletion status: 0.77 (95%CI: 0.73-0.80), 29% (95%CI: 21-40%), and 99% (95%CI: 92-100%), respectively. The T2-FLAIR mismatch sign was an insensitive but highly specific marker for IDHmut-Noncodel and IDH-Mutation LGGs, whereas it was not a useful marker for IDHmut-Codel LGGs. The findings might identify the T2-FLAIR mismatch sign as a non-invasive imaging biomarker for the selection of patients with IDH-mutant LGGs. • The T2-FLAIR mismatch sign was not a sensitive sign for IDH mutation in LGGs. • The T2-FLAIR mismatch sign was related to IDHmut-Noncodel with a specificity of 99%. • The pooled specificity (69%) of the T2-FLAIR mismatch sign for IDHmut-Codel was low.

T2 FLAIR Hyperintensity Volume Is Associated With Cognitive Function and Quality of Life in Clinically Stable Patients With Lower Grade Gliomas.

Survival outcomes for patients with lower grade gliomas (LrGG) continue to improve. However, damage caused both by tumor growth and by the consequences of treatment often leads to significantly impaired cognitive function and quality of life (QoL). While neuropsychological testing is not routine, serial clinical MRIs are standard of care for patients with LrGG. Thus, having a greater understanding of MRI indicators of cognitive and QoL impairment risk could be beneficial to patients and clinicians. In this work we sought to test the hypothesis that in clinically stable LrGG patients, T2 FLAIR hyperintensity volumes at the time of cognitive assessment are associated with impairments of cognitive function and QoL and could be used to help identify patients for cognitive and QoL assessments and interventions. We performed anatomical MR imaging, cognitive testing and QoL assessments cross-sectionally in 30 clinically stable grade 2 and 3 glioma patients with subjective cognitive concerns who were 6 or more months post-treatment. Larger post-surgical T2 FLAIR volume at testing was significantly associated with lower cognitive performance, while pre-surgical tumor volume was not. Older patients had lower cognitive performance than younger patients, even after accounting for normal age-related declines in performance. Patients with Astrocytoma, IDH mutant LrGGs were more likely to show lower cognitive performance than patients with Oligodendroglioma, IDH mutant 1p19q co-deleted LrGGs. Previous treatment with combined radiation and chemotherapy was associated with poorer self-reported QoL, including self-reported cognitive function. This study demonstrates the importance of appreciating that LrGG patients may experience impairments in cognitive function and QoL over their disease course, including during periods of otherwise sustained clinical stability. Imaging factors can be helpful in identifying vulnerable patients who would benefit from cognitive assessment and rehabilitation.

An Immune-Related Prognostic Signature for Predicting Clinical Outcomes and Immune Landscape in IDH-Mutant Lower-Grade Gliomas.

Background IDH mutation is the most common in diffuse LGGs, correlated with a favorable prognosis. However, the IDH-mutant LGGs patients with poor prognoses need to be identified, and the potential mechanism leading to a worse outcome and treatment options needs to be investigated. Methods A six-gene immune-related prognostic signature in IDH-mutant LGGs was constructed based on two public datasets and univariate, multivariate, and LASSO Cox regression analysis. Patients were divided into low- and high-risk groups based on the median risk score in the training and validation sets. We analyzed enriched pathways and immune cell infiltration, applying the GSEA and the immune evaluation algorithms. Results Stratification and multivariate Cox analysis unveiled that the six-gene signature was an independent prognostic factor. The signature (0.806/0.795/0.822) showed a remarkable prognostic performance, with 1-, 3-, and 5-year time-dependent AUC, higher than for grade (0.612/0.638/0.649) and 1p19q codeletion status (0.606/0.658/0.676). High-risk patients had higher infiltrating immune cells. However, the specific immune escape was observed in the high-risk group after immune activation, owing to increasing immunosuppressive cells, inhibitory cytokines, and immune checkpoint molecules. Moreover, a novel nomogram model was developed to evaluate the survival in IDH-mutant LGGs patients. Conclusion The six-gene signature could be a promising prognostic biomarker, which is promising to promote individual therapy and improve the clinical outcomes of IDH-mutant gliomas. The study also refined the current classification system of IDH-mutant gliomas, classifying patients into two subtypes with distinct immunophenotypes and overall survival.

NI-13 Prediction of outcome at the time of discontinuing TMZ-adjuvant therapy in IDH-mutant lower grade glioma using 11C-methinine PET

Purpose: This study aimed to clarify whether positron emission tomography with 11C-methyl-L-methionine (11C-met PET) can predict consequential outcomes at the time of discontinuing temozolomide (TMZ)-adjuvant chemotherapy in patients with residual isocitrate dehydrogenase gene (IDH)-mutant lower-grade glioma.Methods: In 30 patients showing residual lesions of IDH-mutant lower grade glioma (16 with diffuse astrocytoma and 14 with anaplastic astrocytoma), we performed 11C-met PET, and calculated the tumor-to-normal brain tissue ratio of standardized uptake values (SUVT/N) at the time of discontinuing TMZ-adjuvant chemotherapy. We determined cutoff values to predict tumor relapse using the receiver operating characteristic curve for various prognostic factors including age, Karnofsky performance scale, number of courses of therapy, residual tumor size, and SUVT/N. The promotor methylation status of O6-methylguanine-DNA methyl-transferase gene (MGMT) was assessed using methylation-specific polymerase chain reaction. Progression-free survival (PFS) was compared between groups divided by cutoff values. Uni- and multivariate analyses were conducted using log-rank testing and Cox regression analysis, respectively.Results: Univariate analysis identified MGMT methylation status (p = 0.04) and an SUVT/N of 1.27 (p = 0.02) as predictors of PFS after TMZ discontinuation. In multivariate analysis, both unmethylated MGMT and SUVT/N ≥ 1.27 remained as strong predictors of unfavorable outcome. Conclusion: The present study suggested that 11C-met PET allows prediction of outcomes comparable to MGMT promotor methylation status at the time of discontinuing TMZ-adjuvant chemotherapy in patients with residual IDH-mutant lower-grade glioma.

EPCO-22. INHERITED POLYMORPHISM IN CHROMOSOME 8Q24 COOPERATES WITH MUTANT IDH1, Trp53 AND ATRX LOSS TO INDUCE LOW-GRADE GLIOMA

Abstract Establishing causal links between genetic polymorphisms and increased heritable risk of developing brain cancer is a major challenge. The non-coding single nucleotide polymorphism rs55705857 (A &amp;gt;G) is associated with a ~6-fold increased risk to develop IDH-mutant low-grade glioma (LGG). The rs55705857 G allele has a minor allele frequency of only ~5% in the general population but is found in ~40% of patients with IDH-mutant LGG and patients carrying risk-alleles are diagnosed on average 7-12 years earlier than those carrying non-risk A alleles. This makes rs55705857 one of the highest reported genetic associations with cancer, comparable with inherited BRCA1 gene mutations and the risk of developing breast cancer or other familial glioma genes such as NF1/2, CDKN2A or p53. To generate a LGG mouse model, we combined clonal activation of IDH1R132H with mutations of Trp53 and Atrx, which resulted in the development of LGG-like brain tumors in 25% of mice. Mutating the highly conserved, orthologous mouse rs55705857 locus to mimic the human risk allele dramatically accelerated tumor development from 463 to 172 days and increased penetrance to 75%. The resulting tumors exhibit elevated R-2-hydroxyglutarate levels, well-differentiated fibrillary neoplastic histology and metabolic rewiring, recapitulating histopathological and molecular hallmarks of human LGG. Mechanistically, we show that the rs55705857 locus resides within a brain-specific enhancer, which shows enhanced activity in IDH-mutant tumors. In addition, we found that the risk allele disrupts OCT2/4 binding, allowing increased interaction with the Myc promoter and increased Myc expression. The hyperactive chromatin status combined with the tissue specificity of this enhancer explains the cooperativity between mutant IDH and rs55705857 and why rs55705857 is associated specifically with IDH-mutant glioma, but not other cancers. Overall, we generated new LGG mouse models, which provide insights into the pathophysiology of this deadly disease and shed light into the heritable predisposition to LGG development.

Assessment of TBK1 as a Novel Therapeutic Target in IDH Wild-Type Gliomas

Previously we identified four putative therapeutic targets in glioma using a high-throughput molecular approach, SHOC2, TBK1, TMED2, and YY1. These targets have been shown to play critical roles in tumor progression via the PI3K-AKT and Ras-ERK pathways. TBK1 was further pursued due to its role in multiple cancer-associated pathways and it was found to be significantly overexpressed in IDH wild-type compared with IDH mutant lower-grade gliomas (LGGs) (P = 0.005). To assess the therapeutic potential of targeting TBK1, we evaluated the efficacy of TBK1 inhibitors and their synergy with temozolomide (TMZ) and/or radiation in preclinical in vitro glioblastoma (GBM) models.LGG patient samples from an institutional cohort and the TCGA (RNA-sequencing) were used for TBK1 expression analyses. Cell viability and colony formation assays were performed using GBM cell lines (LN18, U87, GBM30-luciferase). TBK1 siRNAs and commercially available pharmacologic inhibitors, Amlexanox and GSK8612, were purchased for in vitro studies. Cells were treated with TBK1 inhibitors alone or in combination with radiation and/or TMZ. TBK1, AKT, and ERK expression were evaluated using Western blot analyses RESULTS: TBK1 was found to be significantly upregulated in IDH wild-type versus IDH mutant LGGs. Inhibition of TBK1 by siRNA or pharmaceutical agent (Amlexanox or GSK8612) resulted in decreased cell viability and colony formation in vitro in a dose- and time-dependent manner. Importantly, a synergistic effect was observed when GBM cells were treated with Amlexanox or GSK8612 in combination with TMZ and/or radiation. Further downstream molecular analysis revealed that inhibition of TBK1 led to decreased AKT and ERK activation.In conclusion, our study showed that Amlexanox or GSK8612 was effective in inhibiting TBK1 expression leading to decreased cell proliferation and colony formation in GBM cell lines. A synergistic effect was observed with each of these TBK1 inhibitors plus radiation and/or TMZ. These results suggest that TBK1 may be a potential candidate to pursue as novel therapeutic target in IDH wild-type gliomas. Future work will focus on in vivo studies with Amlexanox or GSK8612 alone and in combination with TMZ and radiation AUTHOR DISCLOSURE: Z. Tong: None.