Gemcitabine With or Without Capecitabine in Treating Patients With Locally Advanced or Metastatic Pancreatic Cancer

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed ductal adenocarcinoma of the pancreas Locally advanced or metastatic disease not amenable to curative surgical resection Macroscopic residual disease after prior resection with histological confirmation is allowed Unidimensionally measurable disease No intracerebral metastases or meningeal carcinomatosis PATIENT CHARACTERISTICS: Age: Over 18 Performance status: WHO 0-2 Life expectancy: More than 3 months Hematopoietic: WBC greater than 3,000/mm3 Neutrophil count greater than 1,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin less than 2 mg/dL Renal: Creatinine less than 2 mg/dL Creatinine clearance greater than 50 mL/min Cardiovascular: No New York Heart Association class III or IV heart disease No uncontrolled angina pectoris Other: No other prior malignancy except nonmelanoma skin cancer or carcinoma in situ of the cervix No other concurrent uncontrolled medical condition No other medical or psychiatric condition that would preclude study No known hypersensitivity to fluorouracil No dihydropyrimidine dehydrogenase deficiency No known malabsorption syndromes Not pregnant or nursing Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy (including preoperative or adjuvant) for this disease No other concurrent cytotoxic chemotherapy Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy (including preoperative or adjuvant) for this disease Surgery: See Disease Characteristics Other: No prior investigational drugs (including preoperative or adjuvant) for this disease No other concurrent investigational drugs No concurrent dipyridamole or allopurinol No concurrent sorivudine or sorivudine analogs (e.g., brivudine) (capecitabine arm only)