Expression of PD-L1 as a predictive marker of sensitivity to immune checkpoint inhibitors in patients with advanced biliary tract cancer. - Kim, Hongsik; Kim, Ryul; Jo, Hyunji; Kim, Hye Ryeon; Hong, Joohyun; Ha, Sang Yun; Park, Joon Oh; Kim, Seung Tae (Therapeutic Advances in Gastroenterology, 2022)