- Arm IV (weeks 5-32): Patients receive MTX IV as in arm II on weeks 7, 10, 13, 24, 27, and 30; leucovorin calcium as in arm I; and pegaspargase, mercaptopurine, IT MTX, dexamethasone, vincristine, daunorubicin, cyclophosphamide, cytarabine, and thioguanine as in arm III.