CD274 and biliary tract cancer: We performed searches of Pubmed/Medline, the Cochrane library, and Scopus using the keywords “biliary tract cancer” OR “intrahepatic cholangiocarcinoma” OR “extrahepatic cholangiocarcinoma” OR “perihilar cholangiocarcinoma” OR “distal cholangiocarcinoma” OR “gallbladder carcinoma” OR “ampulla of Vater” AND “antiangiogenic therapy” AND “immunotherapy” OR “immune checkpoint inhibitors” OR “PD-L1 inhibitors” OR “immunotherapy and antiangiogenic combined therapy”.