PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy No concurrent colony-stimulating growth factors within 24 hours of fluorouracil-uracil Chemotherapy: No more than 1 prior regimen of chemotherapy Prior taxanes and fluorouracil allowed At least 3 weeks since prior chemotherapy (6 weeks for mitomycin or nitrosoureas) and recovered No other concurrent chemotherapy Endocrine therapy: At least 3 weeks since prior hormonal therapy and recovered No concurrent anti-cancer hormonal agents Radiotherapy: At least 3 weeks since prior radiotherapy and recovered Concurrent radiotherapy allowed for palliation of painful bone metastases, pathologic fractures of known lytic disease, or brain lesions Surgery: Not specified Other: At least 3 weeks since prior investigational drugs No concurrent antiarrhythmic medication No other concurrent investigational therapy No concurrent halogenated anti-viral agent (e.g., lodenosine, fialuridine, clevudine, emtricitabine, or sorivudine)