- Patients on both arms without CNS disease at presentation receive CNS prophylaxis comprising methotrexate (MTX) intrathecally (IT) on days 1, 8, 15, and 22. Patients on both arms with CNS disease at presentation receive CNS therapy comprising hydrocortisone (HC) IT and MTX IT alternating with cytarabine (ARA-C) IT twice a week until CSF clears. After induction, patients on both arms proceed to consolidation, regardless of response.