The Range in Overall Survival in IDH-Mutant Glioma Grades 2 and 3 After Radiotherapy With Alkylating Chemotherapy as Reported in Several Larger Series (Source: Bell et al.,12 van den Bent et al.,15 Chang et al.,14 Lassman et al.,11 Minniti et al.17). This evidence concerns the gene IDH1 and central nervous system cancer.