IDH1 and astrocytoma (excluding glioblastoma): Moreover, the use of new brain-penetrant therapies that target the mutant IDH1 and IDH2 enzymes (eg, vorasidenib), is on the rise for the treatment of low-grade IDH-mutant astrocytomas.3 Hence, accurate risk stratification of patients with IDH-mutant astrocytomas is critical in guiding treatment decisions.