CEACAM5 and pancreatic ductal adenocarcinoma: PDAC, pancreatic ductal adenocarcinoma; RPC, resectable pancreatic cancer; BRPC, borderline resectable pancreatic cancer; LAPC, locally advanced pancreatic cancer; MPC, metastatic pancreatic cancer; CA19 − 9, carbohydrate antigen 19 − 9; CEA, carcinoembryonic antigen.