MGMT and intrahepatic cholangiocarcinoma: 5‐FU, 5‐fluorouracil; dCCA, distal cholangiocarcinoma; ECOG PS, Eastern Cooperative Oncology Group Performance Status; iCCA, intrahepatic cholangiocarcinoma; IHC, immunohistochemistry; IQR, interquartile range; MGMT, O6‐methylguanine DNA methyltransferase; NA, not available; pCCA, perihilar cholangiocarcinoma.