Recurrent glioblastoma (GBM) is characterized by a dismal prognosis, with a median overall survival of 6-9 months. While a standard of care is established for the initial treatment of GBM - radiation with concurrent and adjuvant temozolomide chemotherapy - management of recurrent disease remains suboptimal. Treatment options include repeat surgery, re-irradiation, or chemotherapy (including experimental targeted therapies, biologic agents, and immunotherapies). Only a minority of patients has response to these treatments, and the resultant benefits in progression-free and overall survival are on the order of weeks to months.