8. Patients with histologically proven intracranial glioblastoma, gliosarcoma or anaplastic astrocytoma will be eligible. Patients must have shown unequivocal radiographic evidence for tumor progression by MRI scan. A scan should be performed within 14 days prior to registration and on a steroid dose that has been stable for at least 5 days. If the steroid dose is increased between the date of imaging and registration, a new baseline MRI is required.