Carcinoembryonic Antigen (CEA) Biomarker
What is the CEA biomarker?
Carcinoembryonic Antigen (CEACAM5), also called CEA, is a protein coated with sugar that is very important for communication between cells in embryos during their development in the womb. After birth, CEA is barely detectable in healthy people. In colorectal cancer patients, CEA levels are abnormally high, and the protein can be detected in the blood. Doctors are using CEA in the blood as a biomarker because the higher the CEA levels are, the faster the cancer is growing. CEA levels are expected to go down in patients who had a surgery to remove their tumor.
When and how should I have CEA biomarker testing?
Your doctor will test your blood for CEA levels after you are diagnosed with colorectal cancer, during treatment, and during follow-up visits.
- If you were diagnosed at an early stage and are having surgery, your doctor will test your CEA levels before and after surgery and during your follow-up visits: every 3-6 months during the first 2 years, every 6 months during the following 3 years, and every year afterwards to make sure your cancer is not coming back.
- If you were diagnosed with locally advanced cancer and are treated with chemotherapy before or after your surgery, your doctor will test your CEA levels during the course of treatment to make sure the treatment is effective, killing the cancer cells.
- If you were diagnosed with metastatic disease, your doctor will test your CEA levels during the course of treatment to make sure your treatments are effective, killing the cancer cells.
What do I do with this information?
Knowing the details of tumor biomarkers can help you and your doctor make decisions about personalized treatment with therapies tailored specifically to the characteristics of your tumor.
- If your CEA levels do not go down after surgery, it could mean that you may have a second tumor in your colon or rectum or that your cancer has spread to other parts of the body (usually in the liver or in the lungs)1,4. You and your doctor may have to decide on a new course of treatment.
- If your CEA levels went down after surgery but then went up during your follow-up visits, it could mean that your tumor came back. To confirm that cancer came back (recurrence), it is important to repeat the test and also use imaging, such as a chest X-ray, abdominal ultrasound, abdominal CT for colon cancer, or a combined pelvic and abdominal CT for rectal cancer. A colonoscopy could also be used.
- If your CEA levels do not go down during chemotherapy, it could mean that the cancer is aggressive, and the current treatment is not controlling the growth. You and your doctor may have to decide on a new course of treatment.
Limitations of CEA testing
While the CEA biomarker testing is a very common procedure for detection of colorectal cancer growth and division, it has some limitations because the results are not always 100% correct.
- If CEA is negative, it does not guarantee that the cancer has not come back.
- If CEA is positive, it does not mean that the cancer has come back. Test results may need to be repeated or confirmed by additional tests.
For more on side effects of other chemotherapy regimens, click here.
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