There were no significant differences in age, sex, extent of resection, first line treatment (either CCRT or RT alone/RT plus temozolomide), total radiation dose, isocitrate dehydrogenase 1 (IDH1) mutation status, and MGMT methylation status between patients with recurrent GBM and those with RN within both training and test sets. This evidence concerns the gene IDH1 and glioblastoma.