MGMT and intrahepatic cholangiocarcinoma: MASTER: Molecularly Aided Stratification for Tumor Eradication Research; eCCA: extrahepatic cholangiocarcinoma; iCCA: intrahepatic cholangiocarcinoma; IQR: interquartile range; MGMT: O6‐methylguanine DNA methyltransferase; NA: not available; NOS: not otherwise specified.