Daniel J. Brat1 · Kenneth Aldape2 · Howard Colman3 · Dominique Figrarella‐Branger4 · Gregory N. Fuller5 · Caterina Giannini6 · Eric C. Holland7 · Robert B. Jenkins6 · Bette Kleinschmidt‐DeMasters8 · Takashi Komori9 · Johan M. Kros10 · David N. Louis11 · Catriona McLean12 · Arie Perry13 · Guido Reifenberger14,15 · Chitra Sarkar16 · Roger Stupp17 · Martin J. van den Bent18 · Andreas von Deimling19,20 · Michael Weller21

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cIMPACT-NOW update 5: recommended grading criteria and terminologies for IDH-mutant astrocytomas.

In the 2016, WHO classification of tumors of the central nervous system, isocitrate dehydrogenase (IDH) mutation is a main classifier for lower grade astrocytomas and IDH-mutated astrocytomas is now regarded as a single group with longer survival. However, the molecular and clinical heterogeneity among IDH mutant lower grade (WHO Grades II/III) astrocytomas have only rarely been investigated. In this study, we recruited 160 IDH mutant lower grade (WHO Grades II/III) astrocytomas, and examined PDGFRA amplification, CDKN2A deletion and CDK4 amplification by FISH analysis, TERT promoter mutation by Sanger sequencing and ATRX loss and p53 expression by immunohistochemistry. We identified PDGFRA amplification, CDKN2A homozygous deletion and CDK4 amplification in 18.8%, 15.0% and 18.1% of our cohort respectively, and these alterations occurred in a mutually exclusive fashion. PDGFRA amplification was associated with shorter PFS (P = 0.0003) and OS (P < 0.0001). In tumors without PDGFRA amplification, CDKN2A homozygous deletion or CDK4 amplification was associated with a shorter OS (P = 0.035). Tumors were divided into three risk groups based on the presence of molecular alterations: high risk (PDGFRA amplification), intermediate risk (CDKN2A deletion or CDK4 amplification) and low risk (neither CDKN2A deletion and CDK4 amplification nor PDGFRA amplification). These three risk groups were significantly different in overall survival with mean survivals of 40.5, 62.9 and 71.5 months. The high-risk group also demonstrated a shorter PFS compared to intermediate- (P = 0.036) and low-risk (P < 0.0001) groups. One limitation of this study is the relatively short follow-up period, a common confounding factor for studies on low-grade tumors. Our data illustrate that IDH mutant lower grade astrocytomas is not a homogeneous group and should be molecularly stratified for risk.

IDH mutant lower grade (WHO Grades II/III) astrocytomas can be stratified for risk by CDKN2A, CDK4 and PDGFRA copy number alterations

Gliomas are the most common central nervous system tumors. New technologies, including genetic research and advanced statistical methods, revolutionize the therapeutic approach to the patient and reveal new points of treatment options. Moreover, the 2021 World Health Organization Classification of Tumors of the Central Nervous System has fundamentally changed the classification of gliomas and incorporated many molecular biomarkers. Given the rapid progress in neuro-oncology, here we compile the latest research on prognostic and predictive biomarkers in gliomas. In adult patients, IDH mutations are positive prognostic markers and have the greatest prognostic significance. However, CDKN2A deletion, in IDH-mutant astrocytomas, is a marker of the highest malignancy grade. Moreover, the presence of TERT promoter mutations, EGFR alterations, or a combination of chromosome 7 gain and 10 loss upgrade IDH-wildtype astrocytoma to glioblastoma. In pediatric patients, H3F3A alterations are the most important markers which predict the worse outcome. MGMT promoter methylation has the greatest clinical significance in predicting responses to temozolomide (TMZ). Conversely, mismatch repair defects cause hypermutation phenotype predicting poor response to TMZ. Finally, we discussed liquid biopsies, which are promising diagnostic, prognostic, and predictive techniques, but further work is needed to implement these novel technologies in clinical practice.

Prognostic and Predictive Biomarkers in Gliomas.

Patient-based cancer models are essential tools for studying tumor biology and for the assessment of drug responses in a translational context. We report the establishment a large cohort of unique organoids and patient-derived orthotopic xenografts (PDOX) of various glioma subtypes, including gliomas with mutations in IDH1, and paired longitudinal PDOX from primary and recurrent tumors of the same patient. We show that glioma PDOXs enable long-term propagation of patient tumors and represent clinically relevant patient avatars that retain histopathological, genetic, epigenetic, and transcriptomic features of parental tumors. We find no evidence of mouse-specific clonal evolution in glioma PDOXs. Our cohort captures individual molecular genotypes for precision medicine including mutations in IDH1, ATRX, TP53, MDM2/4, amplification of EGFR, PDGFRA, MET, CDK4/6, MDM2/4, and deletion of CDKN2A/B, PTCH, and PTEN. Matched longitudinal PDOX recapitulate the limited genetic evolution of gliomas observed in patients following treatment. At the histological level, we observe increased vascularization in the rat host as compared to mice. PDOX-derived standardized glioma organoids are amenable to high-throughput drug screens that can be validated in mice. We show clinically relevant responses to temozolomide (TMZ) and to targeted treatments, such as EGFR and CDK4/6 inhibitors in (epi)genetically defined subgroups, according to MGMT promoter and EGFR/CDK status, respectively. Dianhydrogalactitol (VAL-083), a promising bifunctional alkylating agent in the current clinical trial, displayed high therapeutic efficacy, and was able to overcome TMZ resistance in glioblastoma. Our work underscores the clinical relevance of glioma organoids and PDOX models for translational research and personalized treatment studies and represents a unique publicly available resource for precision oncology.

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Patient-derived organoids and orthotopic xenografts of primary and recurrent gliomas represent relevant patient avatars for precision oncology.

The most recent cIMPACT-NOW update highlighted the homozygous deletion of the Cyclin Dependent Kinase Inhibitor 2A (CDKN2A) gene as a clinically important molecular alteration in IDH-mutant glioma. Correspondingly, we systematically reviewed the contemporary literature to affirm the contemporary stance of the literature on the prognostic significance of this alteration in this setting based on the current World Health Organization (WHO) Grade classification. A systematic search of seven electronic databases from inception to February 2020 was conducted following PRISMA guidelines. Articles were screened against pre-specified criteria to include lower-grade glioma (LGG, WHO Grade II/III) and glioblastoma (GBM, WHO Grade IV) separately. Progression free survival (PFS) and overall survival (OS) from Kaplan–Meier and multivariable analyses were outcomes of interest. Nine institutional studies describing 2193 IDH-mutant gliomas satisfied criteria for evaluation, with 1756 (80%) LGG and 437 (20%) GBM. When reported, the proportion of CDKN2A homozygous deleted gliomas ranged from 9 to 43%, with a median incidence of 22%. For LGG, Kaplan–Meier analyses demonstrated shorter PFS in the presence of CDKN2A homozygous deletion in three studies (median values, 31 versus 91 months), and shorter OS in five studies (median values, 61 versus 154 months). For GBM, Kaplan–Meier analyses demonstrated shorter PFS in the presence of CDKN2A homozygous deletion in two studies (median values, 16 versus 30 months), and shorter OS in four studies (median values, 38 versus 86 months). By multivariable analyses, CDKN2A homozygous deletion was a predictor of significantly shorter PFS and OS in both LGG and GBM across all included studies. The CDKN2A homozygous deletion is an important prognostic factor for survival outcomes of IDH-mutant glioma patients across multiple histologic WHO grades with specific molecular features likely dependent on IDH-mutant status. Greater understanding of how identifying this deletion can assist in the stratification of management for these tumors to optimize clinical course is required.

The prognostic significance of CDKN2A homozygous deletion in IDH-mutant lower-grade glioma and glioblastoma: a systematic review of the contemporary literature

Pediatric low-grade gliomas (PLGGs) consist of a number of entities with overlapping histological features. PLGGs have much better prognosis than the adult counterparts, but a significant proportion of PLGGs suffers from tumor progression and recurrence. It has been shown that pediatric and adult low-grade gliomas are molecularly distinct. Yet the clinical significance of some of newer biomarkers discovered by genomic studies has not been fully investigated. In this study, we evaluated in a large cohort of 289 PLGGs a list of biomarkers and examined their clinical relevance. TERT promoter (TERTp), H3F3A and BRAF V600E mutations were detected by direct sequencing. ATRX nuclear loss was examined by immunohistochemistry. CDKN2A deletion, KIAA1549-BRAF fusion, and MYB amplification were determined by fluorescence in situ hybridization (FISH). TERTp, H3F3A, and BRAF V600E mutations were identified in 2.5, 6.4, and 7.4% of PLGGs, respectively. ATRX loss was found in 4.9% of PLGGs. CDKN2A deletion, KIAA1549-BRAF fusion and MYB amplification were detected in 8.8, 32.0 and 10.6% of PLGGs, respectively. Survival analysis revealed that TERTp mutation, H3F3A mutation, and ATRX loss were significantly associated with poor PFS (p < 0.0001, p < 0.0001, and p = 0.0002) and OS (p < 0.0001, p < 0.0001, and p < 0.0001). BRAF V600E was associated with shorter PFS (p = 0.011) and OS (p = 0.032) in a subset of PLGGs. KIAA1549-BRAF fusion was a good prognostic marker for longer PFS (p = 0.0017) and OS (p = 0.0029). MYB amplification was also a favorable marker for a longer PFS (p = 0.040). Importantly, we showed that these molecular biomarkers can be used to stratify PLGGs into low- (KIAA1549-BRAF fusion or MYB amplification), intermediate-I (BRAF V600E and/or CDKN2A deletion), intermediate-II (no biomarker), and high-risk (TERTp or H3F3A mutation or ATRX loss) groups with distinct PFS (p < 0.0001) and OS (p < 0.0001). This scheme should aid in clinical decision-making.

Wen cai Li

Papers

IDH mutant lower grade (WHO Grades II/III) astrocytomas can be stratified for risk by CDKN2A, CDK4 and PDGFRA copy number alterations

Pediatric low-grade gliomas can be molecularly stratified for risk.