OUTLINE: Induction therapy: Patients receive methotrexate (MTX) IV over 2 hours once on weeks 1, 3, 5, and 7. Patients who respond to treatment receive a fifth dose of MTX on week 9 followed by cytarabine (ARA-C) IV over 3 hours beginning 3 days after completion of MTX infusion and continuing daily for 2 days. Filgrastim (G-CSF) is administered daily beginning 2 days after completion of ARA-C infusion and continuing until harvest of peripheral blood stem cells (PBSC). Patients receive a second course of ARA-C IV beginning 1 month after completion of the first course of ARA-C and continuing daily for 2 days. G-CSF is then administered daily for about 2 weeks. High-dose chemotherapy/transplantation: Patients with stable or responding disease after induction therapy receive high-dose carmustine IV over 1-2 hours on day -7, etoposide IV over 1 hour every 12 hours and ARA-C IV every 12 hours on days -6 to -3, and melphalan IV on day -2. PBSC are reinfused on day 0. Patients receive G-CSF beginning on day 1 and continuing until blood counts recover. Patients are followed monthly for 3 months, every 3 months for 9 months, every 4 months for 1 year, every 6 months for 3 years, and then annually thereafter.