Prognostic value of geriatric nutritional risk index for patients with biliary tract cancer undergoing surgical resection – a single-institution retrospective cohort study - Ikuta, Shinichi; Nakajima, Takayoshi; Fujikawa, Masataka; Aihara, Tsukasa; Yamanaka, Naoki (Contemporary Oncology/Współczesna Onkologia, 2023)