CEACAM5 and adenocarcinoma: 2007). CEA serves as a broad‐spectrum tumour marker, notably aiding in the diagnosis of adenocarcinoma (Senhorello et al. 2020). In metastatic HBC, the concentration of CEA is closely correlated to therapeutic responses (Hao et al. 2019). Expect for monitoring tumourigenesis and therapeutic responses, it is also used to determine the prognosis in human medicine (Hing et al. 2020).