THEantigen tumor 19-9 (or CA 19-9, Cancer Antigen 19-9) is a protein present in small amounts on the surface of some cancer cells. 

CA 19-9 is also present in trace amounts in the pancreas, liver gallbladder, but also the lungs of healthy adults.

The CA 19-9 test can be used to check the patient’s response to treatment for pancreatic (or bile duct) cancer, especially in the advanced stage. The goal is to make sure the treatment is working, or to detect if the cancer continues to grow or even comes back.

It should be noted that the CA 19-9 assay is not used to diagnose pancreatic cancer since it is not specific for this cancer, nor to make an early detection of it.

The examination consists of taking a sample of venous blood, usually taken from the fold of the elbow. The assay is based on the use of an anti-CA 19-9 antibody capable of recognizing the protein present in the patient’s serum.

The concentration of CA 19-9 is considered normal when it is less than 37 U / ml (units per milliliter). Note that this threshold may vary slightly depending on the laboratories performing the analyzes.

In the case of pancreatic cancer, the drop in the level of CA 19-9 means that the treatment is showing some effectiveness. On the contrary, if the level of CA 19-9 increases, it means that the cancer is still progressing or that it has come back (this is called a recurrence). Note that a slight increase in the level of CA 19-9 is not necessarily a bad sign. Rather, the physician observes the increasing trend over time.

A rise in CA 19-9 levels can also be a sign of non-cancerous conditions:

– liver disease (cirrhosis, hepatitis)

—  inflammation of the gallbladder

—   kidney stones

—   inflammation of the pancreas

—   cystic fibrosis, also called cystic fibrosis (a genetic disease that affects the respiratory and digestive tracts)

—   or some pulmonary, renal or gastrointestinal disorders

It can also be a sign of cancers:

—   pancreatic cancer (especially in the advanced stage, the level of CA 19-9 is not particularly high in the early stage)

—   but also colorectal cancer or cancer of the liver, bile ducts, lung, uterus, breast, ovary