Patients with residual disease after completion of arm I or II treatment undergo radiotherapy to areas of bulk disease if feasible. Patients on both arms with meningeal involvement receive ARA-C intrathecally (IT) alternated with MTX every other day until 1 week after clearing of CNS disease and then 2 IT injections during every course of chemotherapy thereafter. Patients with divergent histology who achieve complete response after completion of arm I or II treatment receive interferon alfa 3 times a week for 1 year.