After the 8 courses, monthly maintenance chemotherapy plus imatinib mesylate will be given. This includes daily imatinib mesylate, monthly vincristine by vein, and prednisone by mouth for 5 days every month. Maintenance chemotherapy will be given for a total of 24 months, and will be interrupted by 2 periods of intensive chemotherapy courses with hyper-CVAD and imatinib mesylate at 6 and 13 months from the start of maintenance. Imatinib mesylate will be continued daily as tolerated indefinitely.