A meta-analysis of published studies showed that MGMT promoter methylation was associated with better PFS (HR = 0.51; 95% CI: 0.38–0.69) and OS (HR = 0.49; 95% CI: 0.38–0.64) in patients with GBM regardless of therapeutic intervention and associated with longer OS (HR = 0.42; 95% CI: 0.29–0.60) in GBM patients treated with alkylating agents [32]. The gene discussed is MGMT; the disease is glioblastoma.