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The current World Health Organization (WHO) brain tumor classifications already incorporate one molecular feature (CDKN2A/B homozygous deletion) that can upgrade an IDH-mutant astrocytoma to grade 4, even in the absence of classic high-grade histologic features. However, this new study shows there are several additional molecular alterations that independently predict worse survival in IDH-mutant astrocytoma and therefore may warrant inclusion in grading criteria.
Across two large cohorts of roughly 1,200 patients, the authors found that CDK4 amplification, CCND2 amplification, PDGFRA alterations, PIK3R1 mutations, MYCN amplification, and EGFR alterations are all associated with significantly poorer outcomes in IDH- mutant astrocytoma. This is important, because roughly 18% of tumors currently classified as grade 2 or 3 harbor at least one of these high-risk molecular features.
Clinically, these tumors fall into an intermediate-risk category, with survival outcomes worse than standard grade 2 or 3 tumors but still better than grade 4 disease. Median overall survival in this group was approximately 67 to 82 months, compared to 135 to 141 months for typical grade 2 or 3 tumors and 35 to 45 months for grade 4 tumors.
For patients, the key implication is that a tumor labeled as grade 2 or 3 may still behave more aggressively if these molecular features are present. For clinicians, the findings support consideration of expanding molecular grading criteria to include these additional alterations, as they provide independent prognostic value, help identify patients who may benefit from closer monitoring or more aggressive upfront treatment, and improve risk stratification for clinical trials.