MGMT and glioblastoma: A 2011 retrospective study showed the MGMT promoter methylation was the strongest favorable predictor for overall survival in unresectable glioblastoma patients (OS, median: 20.3 vs. 7.3 months, p < 0.001, HR 0.30, 95% CI 0.16–0.55), and PFS (median: 15.0 vs. 6.1 months, p < 0.001, HR 0.31, 95% CI 0.17–0.57) and was also associated with higher frequencies of treatment response and prolonged post-recurrence survival (PRS, median: 4.5 vs. 1.4 months, p < 0.002, HR 0.39, 95% CI 0.21–0.71) [13].