OBJECTIVES: I. Assess remission rates and overall and progression-free survival in patients with Waldenstrom's macroglobulinemia treated with tandem high dose melphalan supported by peripheral blood stem cell support. II. Assess the associated hematologic and nonhematologic toxicities of this regimen in these patients.

OUTLINE: Regimen A (dexamethasone induction): All patients receive high dose dexamethasone orally on days 1-4, 9-12, and 17-20; courses repeat every 35 days for a total of 3 courses. Regimen B (stem cell mobilization and collection): Following a 4-6 week break after dexamethasone induction and regardless of response or progression, patients have stem cells collected following administration of filgrastim (G-CSF) by injection; G-CSF continues until completion of stem cell collection (maximum of 6 aphereses). Regimen C (first peripheral blood stem cell transplant (PBSCT)): Regardless of disease progression, patients recovered from toxicities from dexamethasone induction and stem cell mobilization and collection, and who have adequate number of CD34 cells collected for at least 1 transplant, receive 1 dose of melphalan daily for 2 days followed by peripheral stem cell reinfusion. G-CSF is given by injection beginning on the day after peripheral stem cell reinfusion and continues until the absolute granulocyte count is greater than 1,000/mm3 on 3 consecutive days. Regimen D (second PBSCT): Patients who had adequate stem cell collection for 2 transplants during regimen B, have no evidence of disease progression after the first transplant, and have recovered from effects of previous treatment undergo a second treatment with high dose melphalan with PBSCT and G-CSF support, given 3-12 months following the first transplant. Patients who had enough cells collected for only one transplant go directly to regimen E. Regimen E (maintenance interferon alfa): Beginning 5-12 weeks after transplant and upon hematologic recovery of blood counts and other toxicities, patients with at least a partial response after high dose melphalan and PBSCT receive subcutaneous interferon alfa injections 3 times a week for 5 years or until disease progression, relapse, or toxicity. Patients are followed every month for 6 months, then every 3 months for 5 years, then annually thereafter.

PROJECTED ACCRUAL: A total of 60 patients will be accrued for this study over 4 years.