- Group 1 (average-risk): Patients receive filgrastim (G-CSF) subcutaneously (SC) or IV daily until peripheral blood stem cells (PBSC) are harvested. PBSC are harvested when blood counts recover. Patients then receive craniospinal irradiation (CSI) 5 days a week for 6 weeks. Beginning 6 weeks after completion of CSI, patients receive high-dose chemotherapy comprising vincristine IV followed by cisplatin IV over 6 hours on day -4 and cyclophosphamide IV over 1 hour on days -3 and -2. Patients receive amifostine IV over 1 minute a maximum of 5 minutes prior to cisplatin infusion and then 3 hours into cisplatin infusion. PBSC are reinfused on day 0. Patients receive G-CSF SC beginning on day 1 and continuing for a minimum of 7 days or until blood counts recover. Vincristine IV is administered on day 6. G-CSF is stopped 48 hours prior to beginning subsequent courses of chemotherapy. High-dose chemotherapy repeats every 4 weeks for 4 courses.