MGMT and glioblastoma: Apart from salvage treatment strategies, several factors—including patient age, Karnofsky Performance Status (KPS), O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status, Ki-67 labeling index, and progression-free survival (PFS; the interval between initial therapy and recurrence)—are critical determinants of prognosis in patients with recurrent glioblastoma [19].