MGMT and neoplasm: Age at reirradiation, Karnofsky performance status (KPS), tumor grade (grade III versus grade IV glioma) are well recognized prognostic factors associated with longer survival, whereas the role of other factors, including tumor volume, surgery before reirradiation, time interval from first course of RT, use of concurrent systemic therapy, and MGMT promoter methylation remains controversial [43, 54, 56–58, 64, 69, 71, 74, 75, 80–85].