If you have not been previously treated, on Days 1, 15, and 29 of Cycles 1-4, you will also receive methotrexate and cytarabine. Methotrexate and cytarabine will be given intrathecally (by spinal tap) during a short infusion. If you are found to have disease in the brain/spinal cord, you may need to receive more doses after Cycle 4.