An institutional database was searched for patients with GB defined by histopathology and IDH wild-type astrocytoma with promoter of telomerase reverse transcriptase (ptert) mutations. O6-methylguanine-DNA methyltransferase (MGMT) promotor methylation was analyzed using methylation-specific PCR and Sanger sequencing of CpG sites within the MGMT promotor region. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).