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

RATIONALE: Drugs used in chemotherapy, such as capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving capecitabine after surgery may kill any tumor cells that remain after surgery. Sometimes, after surgery, the tumor may not need more treatment until it progresses. In this case, observation may be sufficient. It is not yet known whether capecitabine is more effective than observation in treating biliary tract cancer. PURPOSE: This randomized phase III trial is studying capecitabine to see how well it works compared with observation in treating patients with biliary tract cancer.