- Induction chemotherapy: Patients receive methotrexate IV over 3 hours on days 1, 10, and 20 and intraventricularly or intrathecally (IT) over 5 minutes on days 1, 5, 10, and 15; oral procarbazine on days 1-7; oral lomustine on day 1; oral dexamethasone every 6 hours on days 1-14 followed by a taper (as tolerated); and cytarabine intraventricularly or IT over 5 minutes on days 1, 5, 10, and 15. Treatment repeats every 42 days for a total of 3 courses. Patients with intraocular lymphoma also receive methotrexate intravitreally twice weekly until the vitreous is clear of cells by slit lamp exam. Patients with stable or responding disease proceed to maintenance therapy.