Gemcitabine With/Out Capecitabine in Locally Advanced, Unresectable, or Metastatic Biliary Cancer

extrahepatic bile duct cancer, gallbladder cancer, liver cancer, adenocarcinoma of the extrahepatic bile duct, unresectable extrahepatic bile duct cancer, recurrent extrahepatic bile duct cancer, adenocarcinoma of the gallbladder, adenocarcinoma with squamous metaplasia of the gallbladder, unresectable gallbladder cancer, recurrent gallbladder cancer, liver and intrahepatic biliary tract cancer, interventional