CA 19-9

What is being analysed?
Cancer antigen 19-9 (CA 19-9) is a protein found on the surface of some cells. This protein does not cause cancer; rather, it is produced by tumour cells, which makes it a useful marker for following the course of the disease.
High CA 19-9 concentrations are found in patients with advanced pancreatic cancer, but they can also be present in other types of cancer, such as bowel, lung and gallbladder cancer, and in conditions such as gallstones, pancreatitis, cystic fibrosis and liver disease. Low CA 19-9 concentrations can also be present in healthy people.

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
CA 19-9 is not sensitive or specific enough to be considered a useful tool for cancer screening.
It is used mainly as a tumour marker to:

• help distinguish cancer of the pancreas and bile ducts from other non-cancerous conditions, such as pancreatitis;
• check the patient’s response to treatment for pancreatic cancer;
• check for recurrence of pancreatic cancer.

CA 19-9 can only be used as a marker if the tumour tissue produces significant amounts of it; if baseline CA 19-9 concentrations are low, the antigen cannot be used as an indicator of the course of the disease.

When is it requested?
CA 19-9 may be requested together with other tests, such as carcinoembryonic antigen (CEA), bilirubin and/or a liver panel, when there are symptoms suggesting pancreatic cancer, such as abdominal pain, nausea, weight loss and jaundice.
If baseline CA 19-9 concentrations are high in pancreatic cancer, periodic checks during treatment make it possible to assess the response to treatment and detect recurrence.

What does the test result mean?
Low CA 19-9 concentrations can be present in a certain percentage of healthy people.
A temporary rise can be caused by many liver and pancreatic diseases.
Moderate to high levels are found in pancreatic cancer, other types of cancer and various diseases. The highest CA 19-9 concentrations are found in cancer of the pancreatic ducts. This is a cancer of the pancreatic tissue that produces digestive enzymes and of the ducts that carry these enzymes to the small intestine. It accounts for 95% of pancreatic cancers.
Periodic CA 19-9 measurements can be useful during and after cancer treatment, because a rise or fall in its levels can indicate whether surgical removal was complete and whether the cancer has come back.

Is there anything else I should know?
Unfortunately early-stage pancreatic cancers give few warning signs. When symptoms and high CA 19-9 concentrations are present, pancreatic cancer is usually already at an advanced stage

1. Why is CA 19-9 not used for screening?
2. What other investigations can be combined with CA 19-9?
3. What are the main risk factors for pancreatic cancer?

1. Why is CA 19-9 not used for screening?
CA 19-9 is not sensitive or specific enough to be recommended as a screening test in people without symptoms: there would be too many false positives and false negatives. Other markers that can identify early-stage pancreatic cancer and are better suited to screening are being sought.

2. What other investigations can be combined with CA 19-9?
Together with CA 19-9, a CT scan, an ultrasound scan, an endoscopic retrograde cholangiopancreatography (a small endoscope is passed through the mouth and stomach into the small intestine) and/or a biopsy to look for cancer cells under the microscope may be requested.

3. What are the main risk factors for pancreatic cancer?
The causes of pancreatic cancer are not yet known. Identified risk factors include smoking, age (mainly people over 50), sex (men are more likely to be affected than women), family history, diabetes, chronic pancreatitis and occupations with heavy exposure to chemicals and dyes