IDH1 and glioblastoma: Interestingly, GBM patients with an oligodendroglial component (n = 57) who survived longer (12 vs. 5.8 months; p = 0.006), comparing to 50 cases of other primary GBM, showed no difference in the frequency of common genetic defects, such as loss of heterozygosity of chromosome 1p/19q, MGMT promoter methylation, or IDH1 mutation [40].