<prompt> True about carcinoembryonic antigen CEA-a Useful for screening of Ca. colonb Gives confirmative evidence of Ca. colonc Helpful for follow-up after resectiond Levels decrease immediately after resection of tumore Tumour size correlates with CEA levelacebdecdeade  <response>: Carcinoembryonic antigen CEACEA is produced by fetal gut, pancrease and liver.It is a glycoprotein.It can be used as a tumor marker in colorectal cancer major use and also in pancreatic, lung, breast, or ovarian carcinoma.It is also increased in some non-neoplastic disorders, e.g. alcoholic cirrhosis, hepatitis, IBD CD, UC, smoking, pancreatitis .Uses of CEA in colon cancerScreeningResponse to surgery after complete surgical resection, CEA should disappear in 6 weeks not immediatly, Persistant beyond 6 week indicates residual tumor.Higher level suggests high tumor burden size Prognostic value.For follow up to see recurrence.CEA assays lack both specificity and sensitivity can not be used to confirm the diagnosis. 