 ARM III: Patients receive vincristine sulfate, dexamethasone, doxorubicin hydrochloride, pegaspargase, methotrexate IT, cyclophosphamide, cytarabine, and thioguanine as in arm I. Patients with intermediate- or high-risk disease CNS1 or CNS2 disease undergo prophylactic CRT 1,200 cGydose QD on days 50-54 and 57-59. 