 3. Performance level: At the time of study enrollment patients must have a Karnofsky greater than or equal to 50 for patients 16 years of age and Lansky greater than or equal to 50 for patients less than or equal to 16 years of age. 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. 