 - Karnofsky 50 for patients 16 years of age and Lansky 50 for patients 16 years of age; note: neurologic deficits in patients with CNS tumors must have been stable or improving for at least 7 days prior to study enrollment; patients who are unable to walk because of paralysis, but who are up in a wheelchair, will be considered ambulatory for the purpose of assessing the performance score 