MGMT and glioblastoma: A comparison of the clinical characteristics between the original 23 GBM patients in the study group and the TCGA cohort used for external validation of the GPI is shown above in Table 1B. There were no statistically significant differences between the two groups except that the proportion of patients with MGMT promotor methylation was significantly higher in the TCGA cohort (44.7% vs. 21.7%; p = 0.04).