IDH1 and glioma: In other words, even in populations analyzed 7 years before the introduction of temozolomide as a second-line drug for GBM in 1999 and as a first-line agent later on and 14 years before the discovery of the importance of the IDH mutation in GBM patients in 2008, some studies were able to establish a strong correlation between the genetic markers of grade 4 gliomas and survival outcome [21,22,23].