Capecitabine or Observation After Surgery in Treating Patients With Biliary Tract Cancer

DISEASE CHARACTERISTICS: Histologically confirmed biliary tract cancer (including intrahepatic or extrahepatic/hilar cholangiocarcinoma or muscle invasive gallbladder cancer or cancer of the distal bile duct) Must have undergone a radical surgical approach which includes liver resection, pancreatic resection, or less commonly both Patients with pathological evidence of microscopic involvement of the margins of the excised specimen are eligible as long as resection is macroscopically complete Must be able to start treatment within 12 weeks of surgery No pancreatic or periampullary cancer No mucosal gallbladder cancer PATIENT CHARACTERISTICS: ECOG performance status 0-2 Urea < 1.5 times upper limit of normal (ULN) Creatinine < 1.5 times ULN Glomerular filtration rate ≥ 60 mL/min (if < 60 mL/min, adequate renal function for capecitabine must be confirmed by isotope EDTA) Hemoglobin ≥ 10 g/dL WBC ≥ 3,000/mm³ Absolute neutrophil count ≥ 1,500/mm³ Platelet count ≥ 100,000/mm³ Bilirubin ≤ 3 times ULN ALT and AST ≤ 5 times ULN Adequate surgical biliary drainage with no evidence of infection Not pregnant or nursing Negative pregnancy test for women of childbearing age and childbearing potential Fertile patients must use effective contraception during study treatment and for at least 3 months after study treatment has ended Must provide written informed consent No history of other malignant diseases within the past 5 years other than adequately treated nonmelanoma skin cancer or in situ carcinoma of the uterine cervix No serious co-existing medical condition likely to interfere with protocol treatment, including a potential serious infection No evidence of significant clinical disorder or laboratory finding that makes it undesirable for the patient to participate in the trial No psychological, familial, sociological, or geographical factors considered likely to preclude study compliance No other serious uncontrolled medical conditions No unresolved biliary tree obstruction PRIOR CONCURRENT THERAPY: See Disease Characteristics Completely recovered from prior surgery No use of other investigational agents within 28 days prior to and during study treatment No prior chemotherapy or radiotherapy for biliary tract cancer No other concurrent anticancer chemotherapy, radiotherapy, or investigational agent