Melphalan, Peripheral Stem Cell Transplantation, and Interleukin-2 Followed by Interferon Alfa in Treating Patients With Advanced Multiple Myeloma

PRIMARY OBJECTIVES: I. Evaluate initial response to therapy, time to disease progression, and overall survival in MM patients treated with melphalan, IL2- incubated peripheral blood stem cells, and sequential IL2. SECONDARY OBJECTIVES: I. Evaluate grade 3-4 toxicities encountered by younger (\< 56 years old) and older (\>56 years old) advanced multiple myeloma patients treated with melphalan, IL2-incubated peripheral blood stem cells, and sequential IL2. OUTLINE: Patients receive melphalan intravenously (IV) over 2-3 hours on day -2 and an infusion of IL-2-treated autologous or syngeneic peripheral blood stem cells on day 0. Beginning on day 0, patients also receive IL-2 IV continuously over 5 days followed by 2 days off. Treatment with IL-2 repeats weekly for 4 weeks. Beginning 1 month later, patients undergo maintenance therapy comprising interferon alfa subcutaneously (SC) 3 times a week in the absence of disease progression or unacceptable toxicity.