Patients receive methotrexate (MTX) intra-arterially over 10 minutes, cyclophosphamide IV over 10 minutes, and etoposide phosphate IV over 10 minutes on days 1 and 2 in conjunction with osmotic blood-brain barrier disruption. Patients also receive oral dexamethasone every 6 hours on days 2-15 (followed by a taper) and intraventricular or intrathecal cytarabine on day 14. Beginning 48 hours after the last dose of MTX, patients receive filgrastim (G-CSF)* subcutaneously once daily for 7-10 days or until blood counts recover. Treatment repeats every 4 weeks for 12 courses in the absence of disease progression or unacceptable toxicity.