PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior interferon At least 2 weeks since prior hematopoietic growth factors (including erythropoietin) Chemotherapy: At least 2 weeks since prior chemotherapy Endocrine therapy: At least 2 weeks since prior steroids Radiotherapy: Not specified Surgery: Not specified Other: At least 2 weeks since prior retinoids