HSV-tk + Valacyclovir + SBRT + Chemotherapy for Recurrent GBM

This is a prospective phase I-II study to assess the efficacy and toxicity of HSV-tk + valacyclovir gene therapy in combination with radiotherapy in recurrent glioblastoma multiforme or anaplastic astrocytoma. This study is comprised of patients who have failed standard of care treatment (maximal safe resection followed by chemoradiation). Clinical response will be evaluated by neurological evaluation, neuropsychological testing, and imaging studies as well as by histological examination wherever a re-operation is clinically indicated. Blood samples will be taken for systemic immunological response, blood counts and liver functions tests. Toxicity will be graded by the Common Terminology Criteria for Adverse Events (CTCAE) and Radiation Therapy Oncology Group (RTOG) neuro-toxicity scores. Patients will also be followed to assess median time to progression and median survival.