A random-effect meta-analysis of the studies with all treatments suggested a significant prognostic impact of MGMT promoter methylation status in older glioblastoma patients (methylated vs. unmethylated: 13 studies, 1119 patients; HR = 0.55, 95% CI 0.42–0.73; test for heterogeneity: Chi2 = 41.75, P<0.0001; I2 = 71%; Fig. S1) [23]–[34]. This evidence concerns the gene MGMT and glioblastoma.