 Patients receive rituximab IV over 5 hours on day 1, mannitol IA, methotrexate IA over 10 minutes, and carboplatin IA over 10 minutes on days 2 and 3. Patients then receive sodium thiosulfate IV over 15 minutes at 4 and 8 hours after carboplatin. Treatment repeats monthly for up to 12 courses in the absence of disease progression or unacceptable toxicity. 