Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed pancreatic cancer

- Stage IV disease

- Measurable disease (≥ 1 cm or > 10 mm lesion(s) by spiral CT scan)

- Disease progression after ≥ 1 gemcitabine-based treatment regimen for
advanced/metastatic disease

- Patient carries the double tandem repeat (S/S) variant of the thymidylate synthase
gene enhancer region (TSER)

- No active CNS metastases (indicated by clinical symptoms, cerebral edema, steroid
requirement, or progressive growth)

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- AST/ALT ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if attributable to liver
metastases)

- Total bilirubin ≤ 1.5 times ULN

- Creatinine normal OR creatinine clearance > 50 mL/min

- Fertile patients must use effective contraception during and for 30 days after
completion of study treatment

- Not pregnant or nursing

- Negative pregnancy test

- Asymptomatic HIV infection allowed

- No recent or ongoing clinically significant gastrointestinal disorder (e.g.,
malabsorption, bleeding, inflammation, emesis, or diarrhea > grade 1)

- Able to swallow capecitabine tablets

- No known hypersensitivity to fluorouracil

- No dihydropyrimidine dehydrogenase (DPD) deficiency

- No clinically significant cardiac disease (e.g., congestive heart failure,
symptomatic coronary artery disease, or cardiac arrhythmias not well controlled with
medication)

- No myocardial infarction within the past 6 months

- No serious, uncontrolled, concurrent infection(s)

- No prior unanticipated severe reaction to fluoropyrimidine therapy

- No other malignancy within the past 5 years except cured nonmelanoma skin cancer or
treated carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- At least 3 weeks since prior chemotherapy

- No prior capecitabine except in the adjuvant setting

- At least 3 weeks since prior radiotherapy or major surgery

- At least 4 weeks since prior participation in any investigational drug study

- At least 4 weeks since prior sorivudine or brivudine

- No concurrent sorivudine or brivudine

- No concurrent cimetidine or azidothymidine (AZT)

- Concurrent radiotherapy for bone pain allowed to a limited field provided ≥ 1
indicator lesion remains outside of the field

- No other concurrent chemotherapy or immunotherapy