PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior interferons, tumor necrosis factor, other cytokines or biologic response modifiers, BCG vaccines, or therapeutic monoclonal antibodies Chemotherapy: See Disease Characteristics Must have completed first line chemotherapy for metastatic disease At least 3 weeks since prior chemotherapy Endocrine therapy: No concurrent corticosteroid, cyclosporine, or adrenocorticotropic hormone therapy Radiotherapy: At least 3 weeks since radiation therapy Surgery: At least 4 weeks since prior surgery requiring general anesthetic No splenectomy Other: At least 4 weeks since other investigational drugs Concurrent bisphosphonate therapy allowed provided therapy was initiated more than 3 weeks prior to study