Capecitabine as Second-Line Therapy in Treating Patients With Stage IV Pancreatic Cancer Who Have the Thymidylate Synthase Gene

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