DISEASE CHARACTERISTICS: Histologically confirmed unresectable or metastatic biliary tract carcinoma (extrahepatic, intrahepatic, or ampulla of Vater) or gallbladder carcinoma Not amenable to combined chemotherapy and radiotherapy CNS metastases that are locally treatable (i.e., lesions treatable with surgery or radiotherapy) allowed if no evidence of progression for at least 4 weeks after completion of treatment