- CNS therapy: Patients receive cytarabine intrathecally (IT) with or without hydrocortisone IT on days 1, 4, and 11 of each induction therapy course. Patients with evidence of CNS involvement by lymphoma continue to receive cytarabine IT twice weekly during any induction therapy treatment delay. Patients who demonstrate CSF clearance receive cytarabine IT once weekly for 4 doses and then once every other week for 4 doses during consolidation therapy. Patients with disease progression during induction therapy or persistent CNS involvement by lymphoma are removed from the study. All other patients proceed to consolidation therapy.