- Arm III (weeks 5-32): Patients receive MTX IV as in arm I on weeks 7, 10, 13, 24, 27, and 30; leucovorin calcium as in arm I; pegaspargase IM on day 2, 3, OR 4 of week 16; and oral mercaptopurine daily on weeks 5-13, and from week 24 until the completion of consolidation therapy. Patients also receive IT MTX as in arm I on weeks 7, 10, 13, 16, 20, 21, and 30; oral dexamethasone twice daily on weeks 8, 16-18, and 28 for a total of 35 days; vincristine IV on day 1 of weeks 8, 9, 16, 17, 18, 28, and 29; daunorubicin IV on day 1 of weeks 16-18; cyclophosphamide IV over 30 minutes on day 1 of week 20; cytarabine IV or subcutaneously daily on days 2-5 of weeks 20 and 21; and oral thioguanine daily on weeks 20-21.