IDH1/2 mutations are found in nearly 80% of secondary glioblastoma (also referred to as IDH-mutant glioblastoma) and in approximately 5% of de novo glioblastoma and are associated with better prognosis.8,9 The DNA repair gene MGMT can be epigenetically silenced through promoter methylation, which renders tumors more susceptible to alkylating agents such as temozolomide. The gene discussed is IDH1; the disease is glioblastoma.