- CNS therapy begins immediately after the end of induction therapy, after remission is documented. This phase of treatment should last 3 weeks and includes a series of spinal taps with the instillation of anti-leukemia drugs. Four spinal taps will be performed over a two-week period. Both groups will receive vincristine, 6-mercaptopurine and methotrexate/cytarabine/hydrocortisone. Patients in the "High Risk" group will also receive doxorubicin with dexrazoxane.