4. Patients must have evidence of tumor progression by contrast enhanced perfusion magnetic resonance imaging (MRI) or computed tomography (CT) scan. This scan should be performed within 14 days prior to registration and on a five-day stable dose of steroids. If the steroid dose is increased between the date of imaging and registration, a new baseline MR/CT is required. The same type of scan (i.e., MRI or CT) must be used throughout the period of protocol treatment for tumor measurement.