IDH1 and oligodendroglioma: A similar effect was also seen for IDH1/2-mutant astrocytoma (non-TCGA cohort status HR: 0.55, P < .01) and IDH1/2-mutant oligodendroglioma (non-TCGA cohort status HR: 0.17, P < .001) even after controlling for features identified above within each glioma subtype.