Maintenance chemotherapy will be given for a total of 30 months, and will be interrupted by 2 periods of intensive chemotherapy courses. The first will be at six months into the maintenance program starting first with hyper-CVAD (like Course 1) except without pegylated asparaginase). The following months, participants will receive methotrexate by vein on Day 1, vincristine by vein on Day 1, and pegylated asparaginase by vein on Day 2. Participants will receive this sequence of 2 chemotherapy courses again 18 months into the maintenance program. Participants with the CD20 marker will receive rituximab during the maintenance chemotherapy (with the vincristine during months 1, 3, 6, 7, 10, 13, 18 & 19).