IDH1 and central nervous system cancer: There is increased interest and understanding of the impact of genetic alteration in IDH1 and 2 genes, which in many cases is a better determinant of outcomes than histologic grades, this has led to changes in the 2016 and now the 2021 World Health Organization (WHO) classification of gliomas.11,12 IDH-mutated GB are typically associated with better prognosis, about 5% of GB are IDH-mutated.13 In our dataset, 5 patients in the TTFields arm and 3 in the control arm had IDH mutations.