* This study has several periods of treatment called phases and uses several different drugs in each phase. The drugs may be given by mouth, into a vein, or into the spinal fluid (called intrathecal chemotherapy). In some individuals this treatment helps prevent leukemia cells from coming back in the spinal fluid and brain. Radiation therapy will also be administered as part of this treatment regimen.
* The treatment program consists of 2-different treatment arms with six separate phases of therapy. The phases of treatment are: (1) Steroid prophase (2) Induction (3) Consolidation I (4) Central nervous system (CNS) therapy (5) Consolidation II (6) Continuation.
* The participants treatment arm will depend on the status of their leukemia at the end of the induction therapy (the second phase of treatment). Arm A: all participants who achieve complete remission after Induction and Arm B: all participants who fail to achieve a complete remission after Induction.
* Steroid Prophase: All participants are involved in this treatment phase which consists of two drugs, one given intravenously (IV) and one given intrathecally. This phase lasts 3 days and the purpose is to collect scientific data that might be useful in the future and to see how steroids work in treating leukemia
* Induction: This phase begins immediately after the steroid prophase and lasts about 1 month. Induction is used to cause a remission. Eight drugs are used during this phase of treatment, and administration is either orally, IV or intrathecal. On day 29, participant's bone marrow and peripheral blood counts will be tested. If they have achieved complete remission or partial remission, they will proceed to the next phase of treatment. If they are not in complete remission, they will receive vincristine by IV on days 32, 39 and 46, until complete remission is achieved. If they do not achieve complete or partial remission by day 53 they will be removed from the study.
* Consolidation I: This phase of treatment begins as soon as there is a documented confirmation that the participant's leukemia is either in complete or partial remission. Treatment in this phase lasts about 7 weeks and is intended to further reduce the number of leukemia cells in the body. This consolidation treatment consists of 3 phases: 1A, 1B and 1C. Each phase involves a three week cycle of chemotherapy. Arm A and Arm B will be assigned according to remission status after induction therapy and will determine the order that the participant follows the Consolidation phases.
* Central Nervous System (CNS) Therapy: CNS therapy begins 3 weeks after the end of Consolidation I therapy and should last 3 weeks. Treatment includes a series of lumbar punctures with the administration of anti-leukemia drug as well as oral drugs and IV drugs. Radiation therapy will also be given during this phase of therapy. The purpose of radiation therapy is to prevent leukemia from coming back in the brain. Radiation therapy will be given in either 8 or 10 daily treatments.
* Consolidation II Therapy: This phase begins as soon as CNS therapy ends and lasts about 27-30 weeks. It consists of cycles of chemotherapy repeated every three weeks along with IV PEG-asparaginase administered every 3 weeks. The cycles will be repeated until the participant receives a total of 10 doses of asparaginase.
* Continuation Therapy: This phase begins after the end of the Consolidation II phase. The goal of this phase is to get rid of all leukemia in the body. It consists of cycles of chemotherapy repeated every three weeks and will last until the participant has been in remission for two years.
* During all phases of treatment, participants will have tests and procedures to monitor their health and for research purposes.
