Triacetyluridine and Fluorouracil Compared With Gemcitabine in Treating Patients With Unresectable Locally Advanced, or Metastatic Pancreatic Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed adenocarcinoma of the pancreas Unresectable locally advanced or metastatic disease Stage II, III, or IV Measurable or evaluable disease No elevated tumor marker (CA 19-9) only No clinically significant third-space fluid accumulation (e.g., ascites or pleural effusion) No carcinoid, islet cell, or lymphoma of the pancreas No prior or concurrent brain or leptomeningeal metastases PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: At least 3 months Hematopoietic: WBC at least 3,500/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 9.5 g/dL Hepatic: Bilirubin no greater than 2.0 mg/dL ALT or AST less than 3 times upper limit of normal (ULN) (5 times ULN if liver metastases present) No uncontrolled hepatic dysfunction Renal: Creatinine less than 2.0 mg/dL No uncontrolled renal dysfunction Cardiovascular: No uncontrolled cardiovascular disease requiring therapy, including the following: Angina Arrhythmias Uncompensated cardiac failure Myocardial infarction within the past 6 months Pulmonary: No uncontrolled pulmonary dysfunction Gastrointestinal: Able to take and/or retain oral medication No uncontrolled malabsorption syndrome or any other condition that would interfere with intestinal absorption Other: No known allergy to fluorouracil (5-FU), gemcitabine, triacetyluridine, or any of their components No dihydropyrimidine-dehydrogenase deficiency No active uncontrolled infection No uncontrolled neurologic or psychiatric dysfunction No other malignancy except previously resected basal cell cancer or curatively resected stage I or less cervical cancer that has been disease free for at least 5 years Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception HIV negative PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy (including immunotherapy) for cancer Chemotherapy: No prior chemotherapy for cancer other than as a radiosensitizer No prior 5-FU or gemcitabine other than as a radiosensitizer No prior triacetyluridine No other concurrent chemotherapy (including leucovorin calcium) for cancer Endocrine therapy: No concurrent hormonal therapy for cancer Concurrent megestrol, oral contraceptives, or postmenopausal estrogen replacement therapy allowed Radiotherapy: Prior radiotherapy allowed No concurrent radiotherapy Surgery: See Disease Characteristics Prior resection of pancreas allowed Other: At least 30 days since prior investigational drug or therapeutic device No other concurrent anticancer therapy No other concurrent investigational drugs or devices No concurrent drugs that would interact adversely with 5-FU or gemcitabine