The prolongation of survival achieved by adding temozolomide to radiotherapy and performing adjuvant chemotherapy with temozolomide is not equally distributed among all patients with GBM, but restricted to those in whose tumors the promoter of the DNA repair enzyme methylguanine-methyltransferase (MGMT) is methylated, allowing the efficacy of alkylating chemotherapy [7, 8]. The gene discussed is MGMT; the disease is glioblastoma.