DISEASE CHARACTERISTICS: Multiple myeloma of any stage that has failed 1 or 2 prior regimens (chemotherapy, biologic therapy, or both, or bone marrow transplantation) Evidence of disease progression required Ineligible for known treatment of higher potential efficacy One of the following protein criteria required: Quantifiable M-components of IgG, IgA, IgD, or IgE Urinary kappa or lambda light chain (Bence-Jones protein) excretion Re-treatment on this protocol allowed if disease relapsed after a complete remission