Inclusion Criteria:

• Histologically confirmed primary high-grade astrocytoma, i.e. anaplastic astrocytoma or glioblastoma multiforme.
• Have a WHO performance status 0-2 and be able to undergo outpatient treatment.
• Age ≥18 years.
• No pregnant or lactating patients can be included.

• Patients must have radiographically documented measurable disease postoperatively. At least one tumor lesion must be unidimensionally measurable as follows:

  • Tumor lesion > 10 mm on conventional MRI scan, T1-weighted series, after intravenous (i.v.) gadolinium chelate contrast.
• All diagnostic radiology studies must be performed within 28 days prior to registration.

• Absence of conditions making MRI scans impossible;

  • Cardiac pacemaker
  • Other ferromagnetic metal implants not authorised for use in MRI such as some types of cerebral aneurysm clips
  • Serious claustrophobia
  • Obesity (> 300 lb., 140 Kg)
• Patients who are receiving corticosteroids have to receive stable or decreasing doses for at least 14 days before entering the trial.
• No prior chemotherapy for high-grade astrocytoma
• Absence of opportunistic infections making temozolomide contraindicated.

• Minimum required laboratory data:

  • Hematology:

    • Absolute granulocytes > 1.0 x 10^9/L
    • Platelets > 100 x 10^9/L

  • Biochemistry:

    • Bilirubin < 1.5 x upper normal limit
    • INR < 1.5
    • Serum creatinine <1.5 x upper normal limit
• Adequate cognitive function in order to give informed consent.
• Absence of any psychological, familial or sociological condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial
• Before patient registration/randomization, written informed consent must be given according to national and local regulations.

Exclusion Criteria:

• Lack of fulfillment of inclusion criteria.