DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed metastatic adenocarcinoma of the pancreas

  • Not amenable to curative radiotherapy or surgery
• Received first-line treatment with a gemcitabine-based regimen
• Measurable liver metastasis, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by conventional techniques OR ≥ 10 mm by spiral CT scan
• No symptomatic brain metastasis unless controlled by corticosteroids
• No uncontrolled ascites requiring drainage ≥ 2 times a week
• No leptomeningeal metastasis

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Karnofsky 70-100%

Life expectancy

• Not specified

Hematopoietic

• Absolute granulocyte count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin ≥ 9.0 g/dL

Hepatic

• Bilirubin ≤ 1.5 times upper limit of normal (ULN)
• ALT and AST ≤ 2.5 times ULN (5 times ULN if due to liver metastases)

Renal

• Creatinine clearance ≥ 60 mL/min

Cardiovascular

• No myocardial infarction within the past 6 months
• No severe/unstable angina
• No New York Heart Association class III or IV congestive heart failure

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 30 days after completion of study treatment
• Able to take oral medications
• No known hypersensitivity to fluorouracil
• No other active malignancies
• No known HIV- or AIDS-related illness
• No other severe acute or chronic medical condition, psychiatric condition, or laboratory abnormality that would preclude study participation
• No chronic diarrhea, constipation (uncontrolled by laxatives), nausea, or vomiting

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent immunotherapy
• No concurrent biologic response modifiers

Chemotherapy

• See Disease Characteristics
• At least 2 weeks since prior first-line gemcitabine-based regimen
• No other concurrent chemotherapy
• No fluoropyrimidine-group antineoplastic drugs within 7 days after completion of study treatment

Endocrine therapy

• See Disease Characteristics
• No concurrent endocrine therapy

Radiotherapy

• At least 2 weeks since prior radiotherapy

• No prior radiotherapy to a target lesion unless the following are true:

  • There is evidence of progressive disease after radiotherapy
  • Target lesion is not the only site of measurable disease
• No concurrent radiotherapy

Surgery

• Not specified

Other

• More than 30 days since prior investigational agents
• No prior second-line therapy
• No concurrent investigational agents

• No concurrent drugs that may interact with S-1, including any of the following:

  • Sorivudine
  • Uracil
  • Cimetidine
  • Leucovorin calcium
  • Dipyridamole
  • Allopurinol
  • Phenytoin
  • Flucytosine
• No concurrent enrollment in another clinical study
• No other concurrent anticancer therapy
• No flucytosine within 7 days after completion of study treatment