With combined analysis of IDH, MGMT and G-CIMP status, it has become clear that the prognostic role of MGMT status in grade III tumors is related to IDH mutated tumors, whereas MGMT methylation status is predictive for benefit to alkylating chemotherapy in the absence of IDH mutations in both grade III and IV gliomas (i.e., high-grade astrocytomas) [121, 128, 132]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).