IDH Wild-type Tumors Research Articles

Malignant astrocytomas of elderly patients lack favorable molecular markers: an analysis of the NOA-08 study collective

The number of patients age >65 years with malignant gliomas is increasing. Prognosis of these patients is worse compared with younger patients. To determine biological differences among malignant gliomas of different age groups and help to explain the survival heterogeneity seen in the NOA-08 trial, the prevalence and impact of recently established biomarkers for outcome in younger patients were characterized in elderly patients. Prevalences of mutations of isocitrate dehydrogenase 1 (IDH1) and histone H3.3 (H3F3A), the glioma cytosine-phosphate-guanine island methylator phenotype (G-CIMP), and methylation of alkylpurine DNA N-glycosylase (APNG) and peroxiredoxin 1 (PRDX1) promoters were determined in a representative biomarker subset (n = 126 patients with anaplastic astrocytoma or glioblastoma) from the NOA-08 trial. IDH1 mutations (R132H) were detected in only 3/126 patients, precluding determination of an association between IDH mutation and outcome. These 3 patients also displayed the G-CIMP phenotype. None of the IDH1 wild-type tumors were G-CIMP positive. Mutations in H3F3A were absent in all 103 patients sequenced for H3F3A. MassARRAY analysis of the APNG promoter revealed generally low methylation levels and failed to confirm any predictive properties for benefit from alkylating chemotherapy. Neither did PRDX1 promoter methylation show differential methylation or association with outcome in this cohort. In a 170-patient cohort from The Cancer Genome Atlas database matched for relevant prognostic factors, age ≥65 years was strongly associated with shorter survival. Despite an age-independent stable frequency of O(6)-methylguanine-DNA methyltransferase (MGMT) promoter hypermethylation, tumors in this age group largely lack prognostically favorable markers established in younger glioblastoma patients, which likely contributes to the overall worse prognosis of elderly patients. However, the survival differences hint at fundamental further differences among malignant gliomas of different age groups.

Identification of Retinol Binding Protein 1 Promoter Hypermethylation in Isocitrate Dehydrogenase 1 and 2 Mutant Gliomas

Mutations in isocitrate dehydrogenase 1 (IDH1) and associated CpG island hypermethylation represent early events in the development of low-grade gliomas and secondary glioblastomas. To identify candidate tumor suppressor genes whose promoter methylation may contribute to gliomagenesis, we compared methylation profiles of IDH1 mutant (MUT) and IDH1 wild-type (WT) tumors using massively parallel reduced representation bisulfite sequencing. Reduced representation bisulfite sequencing was performed on ten pathologically matched WT and MUT glioma samples and compared with data from a methylation-sensitive restriction enzyme technique and data from The Cancer Genome Atlas (TCGA). Methylation in the gene retinol-binding protein 1 (RBP1) was identified in IDH1 mutant tumors and further analyzed with primer-based bisulfite sequencing. Correlation between IDH1/IDH2 mutation status and RBP1 methylation was evaluated with Spearman correlation. Survival data were collected retrospectively and analyzed with Kaplan-Meier and Cox proportional hazards analysis. All statistical tests were two-sided. Methylome analysis identified coordinated CpG island hypermethylation in IDH1 MUT gliomas, consistent with previous reports. RBP1, important in retinoic acid metabolism, was found to be hypermethylated in 76 of 79 IDH1 MUT, 3 of 3 IDH2 MUT, and 0 of 116 IDH1/IDH2 WT tumors. IDH1/IDH2 mutation was highly correlated with RBP1 hypermethylation (n = 198; Spearman R = 0.94, 95% confidence interval = 0.92 to 0.95, P < .001). The Cancer Genome Atlas showed IDH1 MUT tumors (n = 23) to be RBP1-hypermethylated with decreased RBP1 expression compared with WT tumors (n = 124). Among patients with primary glioblastoma, patients with RBP1-unmethylated tumors (n = 102) had decreased median overall survival compared with patients with RBP1-methylated tumors (n = 22) (20.3 months vs 36.8 months, respectively; hazard ratio of death = 2.48, 95% confidence interval = 1.30 to 4.75, P = .006). RBP1 promoter hypermethylation is found in nearly all IDH1 and IDH2 mutant gliomas and is associated with improved patient survival. Because RBP1 is involved in retinoic acid synthesis, our results suggest that dysregulation of retinoic acid metabolism may contribute to glioma formation along the IDH1/IDH2-mutant pathway.

Long-term follow-up results of EORTC 26951: A randomized phase III study on adjuvant PCV chemotherapy in anaplastic oligodendroglial tumors (AOD).

2 Background: AOD are chemotherapy-sensitive tumors especially if 1p/19q co-deleted. Between 1995 and 2002 the EORTC Brain Tumor Group conducted a prospective phase III study on adjuvant procarbazine, CCNU and vincristine chemotherapy (PCV) in AOD. We now present long-term follow-up. Methods: Patients (pts) with locally diagnosed newly diagnosed AOD were randomized between radiotherapy (RT, 33 x 1.8 Gy) and the same RT followed by 6 cycles of standard PCV (RT/PCV). Primary endpoints were overall survival (OS) and progression-free survival (PFS). 1p/19q status, IDH status and MGMT promoter methylation were determined in 300, 167, and 186 pts respectively. Results: Between 1996 and 2002, 368 pts were included. At the time of analysis 281 pts (76.4%) had died. Median PFS after RT/PCV was significantly longer compared to RT alone (24.3 months versus 13.21 months, hazard ratio [HR] 0.66, [95% confidence interval (95% CI) 0.52, 0.83]). More RT arm patients received chemotherapy at progression (75% vs 53%). Median OS was also significantly prolonged in the RT/PCV arm (42.3 months vs 30.6 months for the RT arm, HR 0.75 [95% CI 0.60, 0.95]). 1p/19q co-deleted patients (n = 76) treated with RT/PCV had improved OS compared to RT arm pts (median OS not reached vs 113 months; HR 0.54, p = 0.0487). In the 224 patients without 1p/19q co-deletion the difference in OS was non-significant (OS RT/PCV arm 25 months vs 22 months in the RT arm, HR 0.82, p = 0.18; test for interaction p = 0.22). There was a slight trend towards improved OS in MGMT methylated and IDH mutated tumors versus unmethylated and IDH wild type tumors (Table). Conclusions: The addition of PCV to RT increases PFS and OS in AOD. Pts with 1p/19q co-deletion appear to benefit most from the addition of PCV, with a trend for improved OS in pts with MGMT methylation and IDH mutations. [Table: see text]

IDH1 status and survival benefit from surgical resection of enhancing and nonenhancing tumor in malignant astrocytomas.

2019 Background: The value of maximal safe resection for malignant astrocytic gliomas (AA, WHO Grade III anaplastic astrocytoma and GBM, WHO Grade IV glioblastoma) has sometimes been controversial, because of confounding between measures of surgical resection and other prognostic factors. IDH1 gene mutations are associated with improved survival in glioma patients, and are thought to identify tumors with a distinct molecular evolutionary origin. We sought to determine the prognostic impact of surgical resection on survival after controlling for IDH1 status in malignant astrocytomas. Methods: Clinical parameters including preoperative and postoperative MRI-based tumor volume were recorded prospectively on 407 malignant astrocytoma patients – AA (n=157) and GBM (n=250). IDH1 status was assessed by sequencing and R132H-specific immunohistochemistry. Results: The measures of surgical resection associated with longer survival differed between IDH1 wild-type and mutant tumors. In multivariate analyses of IDH1 wild-type tumors (controlling for age, Karnofsky performance score, tumor location, and tumor grade), residual postoperative enhancement was associated with a median survival of 9.9 mo vs. 17.4 mo with no enhancement (HR=1.73, 95% CI, 1.19-2.52, p=.004). Residual non-enhancing disease, however, was not associated with survival (scored as continuous volumetric cc, 95% CI 0.99-1.01, p=.608). These results are consistent with prior studies of GBM, which are largely IDH1 wild-type lesions (Lacroix et al., J Neurosurg 95:190-8, 2001). In contrast, in IDH1 mutant tumors, both residual enhancing (HR=7.93, 95%CI 1.14-55.22, p=.037) and non-enhancing (HR=1.03, 95% CI 1.01-1.05, p=.005) postoperative tumor burden were associated with worse survival. Conclusions: These data suggest surgical resection in malignant astrocytic gliomas may be individualized based on IDH1 genotype. IDH1 mutant tumors have a better baseline overall prognosis, therefore more aggressive surgery and tolerance of temporary peri-operative neurologic deficits can be weighed in an attempt to gain the additional survival benefit that appears to be associated with reducing non-enhancing tumor burden.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

IDH Mutation and Neuroglial Developmental Features Define Clinically Distinct Subclasses of Lower Grade Diffuse Astrocytic Glioma

Diffuse gliomas represent the most prevalent class of primary brain tumor. Despite significant recent advances in the understanding of glioblastoma [World Health Organization (WHO) IV], its most malignant subtype, lower grade (WHO II and III) glioma variants remain comparatively understudied, especially in light of their notable clinical heterogeneity. Accordingly, we sought to identify and characterize clinically relevant molecular subclasses of lower grade diffuse astrocytic gliomas. We conducted multidimensional molecular profiling, including global transcriptional analysis, on 101 lower grade diffuse astrocytic gliomas collected at our own institution and validated our findings using publically available gene expression and copy number data from large independent patient cohorts. We found that IDH mutational status delineated molecularly and clinically distinct glioma subsets, with IDH mutant (IDH mt) tumors exhibiting TP53 mutations, platelet-derived growth factor receptor (PDGFR)A overexpression, and prolonged survival, and IDH wild-type (IDH wt) tumors exhibiting EGFR amplification, PTEN loss, and unfavorable disease outcome. Furthermore, global expression profiling revealed three robust molecular subclasses within lower grade diffuse astrocytic gliomas, two of which were predominantly IDH mt and one almost entirely IDH wt. IDH mt subclasses were distinguished from each other on the basis of TP53 mutations, DNA copy number abnormalities, and links to distinct stages of neurogenesis in the subventricular zone. This latter finding implicates discrete pools of neuroglial progenitors as cells of origin for the different subclasses of IDH mt tumors. We have elucidated molecularly distinct subclasses of lower grade diffuse astrocytic glioma that dictate clinical behavior and show fundamental associations with both IDH mutational status and neuroglial developmental stage.

Molecular pathogenesis of IDH mutations in gliomas

The isocitrate dehydrogenase 1 (IDH1) or 2 (IDH2) genes are mutated in 50-80% of astrocytomas, oligodendrogliomas or oligoastrocytomas of grades II and III, and secondary glioblastomas; they are, however, seldom mutated in primary glioblastomas and never in other types of glioma. Gliomas with IDH1/2 mutations always harbor either TP53 mutations or total 1p/19q loss. This suggests these two types of tumor may arise from common progenitor cells that have IDH1/2 mutations, subsequently evolving into each tumor type with the acquisition of TP53 mutations or total 1p/19q loss. Survival is significantly longer for patients with IDH-mutated gliomas than for those with IDH-wild type tumors. This observation indicates that IDH status defines biologically different subgroups among gliomas. The molecular pathogenesis of IDH1/2 mutations in the development of gliomas is unclear. The mutated IDH1/2 enzyme generates D-2-hydroxyglutarate. Several theories have been proposed, including: increased angiogenesis because of accumulation of HIF-1α; a glioma CpG island methylator phenotype (G-CIMP) induced by inhibition of TET2; and increased vulnerability to oxidative stress because of depletion of antioxidants. Elucidating the pathogenesis of IDH mutations will aid better understanding of the molecular mechanisms of gliomagenesis and may lead to the development of novel molecular classification and therapy.

Molecular signatures classify astrocytic gliomas by IDH1 mutation status

To identify novel glioma-associated pathomechanisms and molecular markers, we performed an array-based comparative genomic hybridization analysis of 131 diffuse astrocytic gliomas, including 87 primary glioblastomas (pGBIV), 13 secondary glioblastomas (sGBIV), 19 anaplastic astrocytomas (AAIII) and 12 diffuse astrocytomas (AII). All tumors were additionally screened for IDH1 and IDH2 mutations. Expression profiling was performed for 74 tumors (42 pGBIV, 11 sGBIV, 13 AAIII, 8 AII). Unsupervised and supervised bioinformatic analyses revealed distinct genomic and expression profiles separating pGBIV from the other entities. Classifier expression signatures were strongly associated with the IDH1 gene mutation status. Within pGBIV, the rare subtype of IDH1 mutant tumors shared expression profiles with IDH1 mutant sGBIV and was associated with longer overall survival compared with IDH1 wild-type tumors. In patients with IDH1 wild-type pGBIV, PDGFRA gain or amplification as well as 19q gain were associated with patient outcome. Array-CGH analysis additionally revealed homozygous deletions of the FGFR2 gene at 10q26.13 in 2 pGBIV, with reduced FGFR2 mRNA levels being frequent in pGBIV and linked to poor outcome. In conclusion, we report that diffuse astrocytic gliomas can be separated into 2 major molecular groups with distinct genomic and mRNA profiles as well as IDH1 gene mutation status. In addition, our results suggest FGFR2 as a novel glioma-associated candidate tumor suppressor gene on the long arm of chromosome 10.