Cancer antigen CA 19-9 is a protein that exists on the surface of certain cells, acting as a marker and used to identify the course of the cancer. It’s initially found in colorectal cancer patients, but subsequently has been identified and highly associated in patients with pancreatic cancer, as well as stomach, lung, gall bladder, and bile duct cancer.

High levels of CA 19.9 tend to be associated with a more advanced disease in patients suffering from pancreatic cancer. Increased levels of CA 19-9 can also be caused by noncancerous conditions, such as gallstones, pancreatitis, cirrhosis of the liver, cystic fibrosis, and cholecystitis.

What Does the CA 19-9 Test Measure?

Other causes of bile duct blockage can lead to an extreme rise in CA 19-9 levels, which fall when the obstruction is cleared. For this reason, it is advisable to wait two weeks after the blockage has been treated or cleared before testing for levels of CA 19-9. If you are allowed no waiting period before testing, it is important to perform the same test after a two week period to see if the levels of CA 19.9 have decreased, there by concluding whether the cause for increased CA 19-9 was the tumor or the blockage itself. It is important to note that small amounts of CA 19-9 can also be found in healthy individuals.

To test for CA 19-9, you will be required to take a blood test known as a CA 19-9 Radioimmunoassay (RIA) test. This measures the levels of tumor-related antigens (CA 19.9) present in your blood. It is important to remember that not every person suffering from pancreatic cancer, or other cancers related to an increase in CA 19-9, will develop an increase in the antigen. For this reason, the RIA test is not viable in terms of screening or diagnosing for cancer.

When Is CA 19-9 Test Needed?

The CA 19-9 may be applied along with other tests, such as carcinoembryonic antigen (CEA), when a patient is showing signs and symptoms which may signify pancreatic cancer. These symptoms include, but are not limited to, unexplained weight loss, abdominal pain, jaundice, and nausea. If CA 19-9 levels are identified to be elevated in a pancreatic cancer patient, then the test may be ordered throughout the treatment process to enable the practitioner to monitor the treatments progress, and help detect recurrence.

What Can the Test Tell?

If you are deemed to require a test for CA 19-9, it is important to understand what your test results mean to fully understand your results, so consult your doctor.

CA 19-9 is measured in units per milliliter (U/mL). Levels in a healthy individual are generally less than 37 U/mL. It is important to remember that high levels of CA 19-9 do not always mean cancer. Below are some suggestions on what your results could indicate:

• Less than 37 U/mL may indicate that you don’t have cancer, although it is not a certainty.
• CA 19-9 levels above 37 U/mL can be an indication of cancer of the pancreas, lung, liver, colon, stomach, or gallbladder.
• If you have been diagnosed with pancreatic cancer and are receiving treatment, a decrease in CA 19-9 can indicate that the treatment is effective. An increase in CA 19-9 levels can indicate that the treatment is yet to have effect. If levels of CA 19-9 do decrease during treatment, but later increase once again, it may be an indication that your cancer has returned.