DISEASE CHARACTERISTICS: Histologically proven plateau phase multiple myeloma at original diagnosis: Bone marrow plasmacytosis with greater than 10% plasma cells, sheets of plasma cells, or biopsy proven plasmacytoma Must be in stable plateau phase requiring objective response, no evidence of continuing improvement by any criteria, and less than 20% variation in M protein at least 4 weeks prior to study Must have at least one of the following at original diagnosis: M protein in serum or urine X-ray evidence of osteolytic lesion Measurable or evaluable M protein Serum M protein greater than 1.0 g/dL Urine M protein greater than 200 mg/24 hours M protein less than these values will be considered evaluable (serum less than 1 g/dL or urine less than 200 mg/24 hours) Nonsecretory patients are ineligible