- Cranial MRI or contrast CT must have been performed within 21days of study entry; the use of MRI rather than CT is preferred; the same type of scan, i.e., MRI or CT must be used throughout the period of protocol treatment for tumor measurement; if the surgical procedure was a resection, cranial MRI or contrast CT performed with 96 hours of resection is preferred but not required; patients without measurable or assessable disease are eligible