In contrast, IDH1/2 mutations are absent in IDH-wt GBMs (defining the subtype), but in rare IDH-mutant astrocytoma grade 4 (~10% of grade 4 gliomas), they confer greater radiosensitivity and better prognosis (ESCAT I) [53]. This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).