MGMT and glioblastoma: The MGMT promoter methylation is also a significant prognostic factor for temozolomide rechallenge in rGBM (43).The MGMT status is significantly associated with OS in temozolomide-treated PGS patients, yet the frequency of MGMT promoter methylation is significantly low in PGS (26.1%) than GBM (54.6%) (8).