PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biologic therapy and recovered No prior allogeneic, syngeneic, or autologous bone marrow transplantation No prior peripheral blood stem cell transplantation No concurrent biologic therapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosourea or mitomycin) and recovered No concurrent chemotherapy Endocrine therapy: See Disease Characteristics Radiotherapy: At least 4 weeks since prior radiotherapy to at least 25% of bone marrow (including pelvic irradiation) and recovered No concurrent radiotherapy Surgery: Prior major gastrointestinal surgery allowed (e.g., Whipple procedure) Other: At least 4 weeks since any prior investigational therapy At least 24 hours since prior alcohol consumption