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Background: We aimed to evaluate the mutation profile, transcriptional variants, and prognostic impact of the epidermal growth factor receptor (EGFR) gene in isocitrate dehydrogenase (IDH)‐wildtype glioblastomas (GBMs). Methods: We sequenced EGFR, evaluated the EGFR splicing profile using a next‐generation sequencing oncopanel, and analyzed the outcomes in 138 grade IV IDH‐wildtype GBM cases. Results: EGFR mutations were observed in 10% of GBMs. A total of 23.9% of the GBMs showed EGFR amplification. Moreover, 25% of the EGFR mutations occurred in the kinase domain. Notably, EGFR alterations were a predictor of good prognosis (p = 0.035). GBM with EGFR alterations was associated with higher Karnofsky Performance Scale scores (p = 0.014) and lower Ki‐67 scores (p = 0.005) than GBM without EGFR alterations. EGFRvIII positivity was detected in 21% of EGFR‐amplified GBMs. We identified two other EGFR variants in GBM cases with deletions of exons 6–7 (Δe 6–7) and exons 2–14 (Δe 2–14). In one case, the initial EGFRvIII mutation transformed into an EGFR Δe 2–14 mutation during recurrence. Conclusions: We found that the EGFR gene profiles of GBM differ among cohorts and that EGFR alterations are good prognostic markers of overall survival in patients with IDH‐wildtype GBM. Additionally, we identified rare EGFR variants with longitudinal and temporal transformations of EGFRvIII. [ABSTRACT FROM AUTHOR]

Central nervous system tumors are classified based on an integrated diagnosis combining histology and molecular characteristics, including IDH1/2 and H3‐K27M mutations, as well as 1p/19q codeletion. Here, we aimed to develop and assess the feasibility of a glioma‐tailored 48‐gene next‐generation sequencing (NGS) panel for integrated glioma diagnosis. We designed a glioma‐tailored 48‐gene NGS panel for detecting 1p/19q codeletion and mutations in IDH1/2, TP53, PTEN, PDGFRA, NF1, RB1, CDKN2A/B, CDK4, and the TERT promoter (TERTp). We analyzed 106 glioma patients (grade II: 19 cases, grade III: 23 cases, grade IV: 64 cases) using this system. The 1p/19q codeletion was detected precisely in oligodendroglial tumors using our NGS panel. In a cohort of 64 grade Ⅳ gliomas, we identified 56 IDH‐wildtype glioblastomas. Within these IDH‐wildtype glioblastomas, 33 samples (58.9%) showed a mutation in TERTp. Notably, PDGFRA mutations and their amplification were more commonly seen in TERTp‐wildtype glioblastomas (43%) than in TERTp‐mutant glioblastomas (6%) (P =.001). Hierarchical molecular classification of IDH‐wildtype glioblastomas revealed 3 distinct groups of IDH‐wildtype glioblastomas. One major cluster was characterized by mutations in PDGFRA, amplification of CDK4 and PDGFRA, homozygous deletion of CDKN2A/B, and absence of TERTp mutations. This cluster was significantly associated with older age (P =.021), higher Ki‐67 score (P =.007), poor prognosis (P =.012), and a periventricular tumor location. We report the development of a glioma‐tailored NGS panel for detecting 1p/19q codeletion and driver gene mutations on a single platform. Our panel identified distinct subtypes of IDH‐ and TERTp‐wildtype glioblastomas with frequent PDGFRA alterations. [ABSTRACT FROM AUTHOR]