The chemotherapy will alternate between hyper-CVAD plus imatinib mesylate (Courses 1, 3, 5, and 7) and methotrexate/cytarabine plus imatinib mesylate (Courses 2, 4, 6, and 8) to complete a total of 8 courses. G-CSF will be given as in Course 1. Anti-nausea medicine will be given with each course of chemotherapy. The urine will be alkalized to protect the kidneys. Antibiotics will be given by mouth to prevent infection.