A tumour marker is a substance of the blood that appears at a higher level than expected in your blood, in your urine or in a sample of your tissue. They may be produced by the presence of cancerous cells or by perfectly healthy cells.
For pseudomyxoma peritonei (PMP) and appendix cancers, the tumour markers which most specialists will look at are CEA (carcinoembryonic antigen), CA-125 (cancer antigen 125) and CA 19-9 (cancer antigen 19-9). An antigen is a toxin or harmful substance which causes an immune response in your body.
Blood tests may be done:
- to help in the diagnosis of cancer
- to find out if cancer treatment is working
- to find out if cancer has come back (recurred) after treatment
The lab report containing your test results should include the relevant reference range for your test(s). Please check with your doctor or the laboratory that performed the test(s) to obtain the reference range if you don’t have your lab report.
Slight CEA elevations (rarely above 10) can occur in some of benign diseases of the intestine, the pancreas, the liver and the lungs (including liver cirrhosis, chronic hepatitis, pancreatitis, ulcerative colitis, Crohn’s disease, and emphysema). Smokers geneally also have elevated CEA.
A CEA level within the given reference range doesn’t guarantee that cancer (even the kinds known to produce CEA) isn’t present, the test isn’t specific enough for that and therefore the CEA test isn’t useful on its own for diagnostic purposes.
CA125 is usually used as test for ovarian cancer so sometimes men aren’t offered this blood test. Slight elevations can also occur in people with cirrhosis, hepatitis, endometriosis, ovarian cysts, and pelvic inflammatory disease as well as in the first trimester pregnancy.
Non-ovarian malignancies include cervical, liver, pancreatic, lung, colon, stomach, biliary tract, uterine, fallopian tube, breast and endometrial carcinomas. As you can see, it isn’t a very specific test.
Elevated CA 19-9 serum levels can occur as a result of cholestasis, which is described by NICE as an impairment of bile formation and/or bile flow. Elevated values can also found with inflammatory diseases of the gastrointestinal tract or the liver as well as in cystic fibrosis patients. Again, not a specific test.
It’s the marker trend that is significant for those patients for whom markers do move with the presence of tumour. An upward trend can indicate that something may be happening. A downward trend can indicate that the tumour is shrinking. A CT scan may confirm this … sometimes the only way to see if something is happening is to open up and have a look. It’s not an exact science …. yet.