CA 19-9 (carbohydrate antigen 19-9) refers to a blood test that measures presence in your blood of a protein that is shed by cells. The protein can be excessively shed by tumor cells of several cancers including cholangiocarcinoma, so the test is used to help diagnose and monitor our cancer.
CA 19-9 is regularly measured for patients undergoing treatments and those being watched for recurrence. The number can fluctuate, and it can be elevated for non-cancer reasons such as inflammation in the bile ducts or pancreas. To give an example, in my own case, my CA 19-9 steadily rose by small bits throughout my chemo and radiation. I was concerned but one of my doctors told me that he did not worry about CA 19-9 unless there was a “doubling or tripling.”
If your doctors are worried by changes in your CA 19-9, they may repeat the test or send you for follow-up testing, e.g., a scan. But as has been reported by other patients, usually small movements in the test result are not viewed as overly concerning.