- Courses 2, 4, and 6: Patients receive ifosfamide IV over 1 hour daily on days 1-5; vincristine IV over 10 minutes and methotrexate IV over 24 hours on day 1; leucovorin calcium IV over 15 minutes every 6 hours on day 2; cytarabine IV over 2 hours on days 4 and 5 and etoposide IV over 1 hour daily on days 4 and 5; oral dexamethasone daily on days 1-5; and methotrexate and cytarabine intrathecally (IT) on day 1. During course 2, patients receive rituximab IV over 1-4 hours on days 8, 10, and 12. During courses 4 and 6, patients receive rituximab IV over 1 hour on day 8. Patients also receive filgrastim (G-CSF) subcutaneously (SC) beginning on day 7 and continuing until blood counts recover.