After the 8 courses, patients with lymphoblastic lymphoma who had enlarged lymph glands in the mediastinum may receive radiation to the chest. Those participants not needing radiation will proceed to monthly maintenance chemotherapy. This includes daily 6-mercaptopurine taken by mouth, weekly methotrexate by vein or mouth, monthly vincristine by vein, and dexamethasone by mouth for 5 days every month. Participants with lymphoblastic lymphoma will start maintenance chemotherapy after finishing radiation.