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What is the cancer antigen 27.29 (CA 27.29) test for breast cancer?


Updated June 06, 2014

Question: What is the cancer antigen 27.29 (CA 27.29) test for breast cancer?
Cancer antigen 27.29 (CA 27.29) is a blood test that is given specifically for breast cancer. The antigen CA 27.29 is found in the blood of women who have been diagnosed with breast cancer. If your CA 27.29 levels rise, it may indicate that your cancer is progressing or spreading. One version of this test is called the "Truquant BR Radioimmunoassay test."

About Cancer Antigen 27.29 (CA 27.29)

CA 27.29 is a mucus-containing protein that is produced by the MUC-1 gene. Breast cancer cells will shed copies of the CA 27.29 protein in to your bloodstream. During treatment, your levels of CA 27.29 may fall, indicating that your treatment is effectively killing the cancer. If your CA 27.29 levels rise, your cancer may be progressing and it may be necessary to adjust your treatments accordingly.

Do I Need to Take the CA 27.29 Blood Test?
If you have, or think you may have, early stage breast cancer, this test may be performed to help make your diagnosis. If you have already been diagnosed with breast cancer and your cancer cells make this protein, this test may benefit you. Doctors use the CA 27.29 test to monitor your response to treatment if the cancer is still in you and makes this protein. If treatment has been completed, the test may be used to detect early recurrence. In this case, after you have completed treatment, your doctor will test your blood at regular intervals for CA 27.29 and give special attention to any increase in levels. It is not a perfect test, but it is often useful along with other tests, such as imaging, to evaluate recurrence and response to treatment.

Benefits of the CA 27.29 Tumor Marker Test
The CA 27.29 test is used to monitor your:

  • Response to treatment
  • Status of your cancer
  • Possibility of early recurrence
CA 27.29 and Other Cancers and Conditions
Other cancers can produce CA 27.29 (colon, liver, lung, pancreatic, ovarian and prostate), but some non life–threatening conditions may also cause CA 27.29 to show up in your blood (ovarian cysts and benign conditions of the breast, liver and kidneys). Having a rise in your CA 27.29 levels is a cause for concern only if it is taken in to consideration with other test results that indicate a malignant condition.

American Cancer Society. Tumor Markers. What Are Tumor Markers? Revised: 01/04/2006.

American Association for Clinical Chemistry. Lab Tests Online. CA 15-3. Last reviewed on June 24, 2006.

American Society of Clinical Oncology. ASCO Patient Guide: Tumor Markers for Breast Cancer. Last Updated: October 22, 2007.

American Family Physician. Serum Tumor Markers. Greg L. Perkins, M.D., Evan D. Slater, M.D., Georganne K. Sanders, M.D., and John G. Prichard, M.D., Ventura County Medical Center, Ventura, California. Am Fam Physician. 2003 Sep 15;68(6):1075-82.

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