Temozolomide at a dose of, 150-200 mg/m2, will be administered orally, after fasting for one hour, once a day for 5 consecutive days (days 1 through 5) every 4 weeks (plus up to 3 days). The starting dose level of 200 mg/m2 will be used for patients who have not previously received any chemotherapy or at 150 mg/m2 for patients who have received previous chemotherapy.