Malignant gliomas are the most common primary brain tumors, and glioblastoma (GBM) is the most common subtype in adults, representing more than 50% of gliomas. Standard initial treatment for newly diagnosed GBM consists of maximal surgical resection followed by radiotherapy to the tumor bed and chemotherapy with an oral DNA alkylator, temozolomide. However, recurrence is nearly universal despite standard therapy. There is no standard treatment at recurrence. Median survival is about 15 months from diagnosis and 6 months from recurrence. Once patients develop tumor progression, conventional chemotherapy is generally ineffective.