Mutational Characterization of Astrocytoma, IDH-Mutant, CNS WHO Grade III in the AACR GENIE Database

Background/Objectives: Astrocytoma, IDH-mutant, CNS WHO grade 3, is a diffuse glioma with poor prognosis, molecularly defined by IDH mutations and frequently co-occurring TP53 and ATRX alterations. This study aimed to delineate the genomic landscape and identify clinically relevant molecular features of astrocytoma, IDH-mutant, CNS WHO grade 3 using this resource. Methods: Patients in the American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange (AACR Project GENIE) database were selected based on histological diagnosis of “anaplastic astrocytoma”, confirmed IDH1/2 mutation, and exclusion of CDKN2A/B homozygous deletions. We analyzed frequencies of somatic mutations, copy number alterations (CNAs), structural variants (SVs), assessed co-occurrence/exclusivity patterns, and explored associations with available demographic and limited survival data. Results: The most common somatic mutations were in IDH1 (98.0%), TP53 (94.8%), and ATRX (55.2%). The observed ATRX mutation frequency was lower than some historical reports (e.g., ~86%). Other recurrent alterations included phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (6.9%), Notch receptor 1 (NOTCH1) (6.9%), and platelet-derived growth factor receptor alpha (PDGFRA) (mutations 4.3%; CNAs also observed). Conclusions: This study provides a comprehensive genomic characterization of astrocytoma, IDH-mutant, CNS WHO grade 3 using the AACR GENIE database, confirming core mutational signatures while also highlighting potential variations in alteration frequencies, such as for ATRX. The findings establish a valuable real-world genomic benchmark for this tumor type, while promoting the need for continued data integration with robust clinical outcomes to identify actionable prognostic and therapeutic targets.