IDH1 and astrocytoma (excluding glioblastoma): In multivariate analysis, histologic grade (p = 0.0019), homozygous CDKN2A deletion (p = 0.0004), and CIN (p = 0.0320) were significantly associated with impaired survival in IDH-mutant astrocytoma patients, suggesting that these features are independently associated with poor outcomes in this diffuse glioma subset, while factors such as MGMT methylation status, MMR mutation, and IDH1 clonality were not (Fig. 5b).