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CA 27-29

Does this test have other names?

Cancer antigen 27-29

What is this test?

CA 27-29 is a blood test used to monitor certain types of cancer. CA 27-29 is the name of an antigen, which is a substance that stimulates your body's defense system. Certain types of cancer cells release CA 27-29 antigen into the blood. This test measures the levels of CA 27-29 in your blood.

Breast cancer is the cancer most likely to release CA 27-29, and the FDA has approved the CA 27-29 blood test as a way for doctors to monitor people with breast cancer. Antigens like CA 27-29 that provide information about cancer are called tumor markers. 

Why do I need this test?


  • To find out whether your cancer has spread before starting treatment

  • To find out how well your treatment is working


What other tests might I have along with this test?


What do my test results mean?


It's important to know that a positive CA 27-29 test does not mean you have breast cancer or that breast cancer has come back. Your test results can be higher than normal for other types of cancer, such as liver, pancreatic, ovarian, and colorectal cancers. Some conditions that aren't cancer may cause a positive CA 27-29 test. Notably, some people with breast cancer do not have a positive CA 27-29 blood test. 




  •  If your CA 27-29 is 38 U/mL or greater, you may have a condition other than breast cancer that raises CA 27-29. These conditions include other types of cancers, as well as noncancerous breast diseases, cysts of the ovary, and liver disease. When CA 27-29 goes up because of a condition other than cancer, the test is called a false-positive. 

How is this test done?


Does this test pose any risks?


What might affect my test results?

Some noncancerous conditions may cause a false-positive CA 27-29. You may also have a false-positive result if you are exposed to mouse antigens in your environment or if you receive cancer treatments that use mouse antigens.

How do I get ready for this test?

You don't need to prepare for this test.  

Online Medical Reviewer: Sohrabi, Farrokh, MD
Last Review Date: 4/26/2012