Carbohydrate antigen (CA) 19-9 is a tetrasaccharide-rich marker that modifies a Lewis(a) blood group antigen. CA 19-9 has been detected at increased concentrations in patients with colon and pancreatic cancer blood. It is also known to be elevated in esophageal and hepatocellular carcinoma. Many non-malignant conditions are known to elevate CA 19-9 in the blood, including cirrhosis, pancreatitis, and diseases of the bile duct.
Because CA 19-9 is not tissue-specific and may also be elevated in non-malignant states, its utility is not a cancer screening tool in asymptomatic individuals but a management tool in pancreatic cancers. When treating individuals who have been diagnosed with a pancreatic tumor, a baseline level of CA 19-9 may be determined. Following treatment, follow-up testing regimens are used to assess the success of the treatment, as levels of CA 19-9 should decrease in response to the treatment.11
Likewise, subsequent increases or recurrence of elevated CA 19-9 levels in the blood following a period of remission would likely indicate tumor regrowth or metastasis.
