- Chemotherapy: Patients receive O6-benzylguanine IV over 1 hour followed by oral temozolomide once daily on days 1-5. Treatment repeats every 4 weeks for up to 6 courses in the absence of disease progression or unacceptable toxicity. Patients experiencing unacceptable toxicity due to O6-benzylguanine may receive temozolomide alone. Patients not experiencing dose-limiting toxicity and who have at least 5% transduced neutrophils by peripheral blood analysis after course 1 receive escalating doses (intrapatient) of temozolomide during courses 2-6. Some patients undergo second-look surgery after the first course of chemotherapy.