 ARM IV: Patients receive nelarabine, methotrexate, cyclophosphamide, cytarabine, mercaptopurine, vincristine sulfate, and pegaspargase as in arm II. Patients with persistent testicular disease or with DS and testicular disease undergo testicular radiotherapy as in arm II DS patients excluded as of 092910. Once blood counts recover, patients proceed to interim maintenance therapy according to their randomizedassigned arm. Patients not achieving M1 marrow by the end of consolidation therapy are removed from the study. 