One of these tests is the cancer antigen 27.29 (CA 27.29) blood test. This is used to check for an antigen associated with breast cancer. An antigen is a protein on the surface of a cell that serves as an identifier. And CA 27.29 is one of several antigens that healthcare providers use as tumor markers for breast cancer.
The CA 27.29 test is primarily used to monitor stage 4 metastatic breast cancer and less commonly to detect recurrence in people previously treated for early-stage breast cancer. A higher antigen level corresponds to recurrence, and a lower antigen level corresponds to treatment response.
Although the CA 27.29 test was approved by the Food and Drug Administration (FDA) to help monitor people with breast cancer, the antigen can be detected with other cancerous and noncancerous conditions.
Purpose of Test
Tumor markers are substances made either by the body in response to cancer or by the tumor itself. Found in blood, urine, and tissue samples, these markers are signals of specific disease processes. This can help healthcare providers distinguish between the types and/or stages of cancer.
Although CA 27.29 is commonly associated with breast cancer, it may also be found in colon, stomach, liver, lung, pancreatic, ovarian, and prostate cancers. While some tumor marker tests are useful for screening or staging cancer, the CA 27.29 test is limited to the following two functions:
Monitoring progression of metastatic breast cancer, with increasing values corresponding to advancing diseaseMonitoring treatment of metastatic breast cancer, with lowering values corresponding to a positive treatment response
CA 27.29 levels will most likely rise during the first 30–90 days of cancer treatment for some patients. This is because treatment can cause the tumor to release CA 27.29 antigens into the bloodstream. Because of this, your oncologist may wait two to three months after the start of each new treatment to get an accurate test result.
Limitations
Studies have shown that the test results don’t specifically differentiate breast cancer from other causes, including noncancerous causes.
There is currently no evidence showing subsequent improvements in survival or quality of life as a result of this test, according to a 2014 study in the Journal of Cancer.
A 2017 article in the Journal of Oncological Sciences states that because its sensitivity is low and it can’t always specify what it is detecting, it is a better tool for monitoring disease progression and detecting metastases (areas cancer has spread to). It should not be used for diagnosing breast cancer or screening for the disease.
Routine mammography is the preferred method of breast cancer screening, whether for new or recurring disease.
Risks
The CA 27.29 is a blood-based test requiring one full test tube of blood, which is collected with a blood draw. As such, the risks of the test are relatively small. Injection site pain, bruising, or bleeding are possible, as is light-headedness or fainting. Infection is rare, but can occur.
Before the Test
It is rare that the CA 27.29 is ordered on its own. Your oncologist will more than likely order a battery of tests to monitor your cancer or its response to therapy. This may include a complete blood count (CBC), liver functions tests, and kidney function tests. No preparation is needed for any of these tests.
Timing
The blood draw only takes a few minutes to perform. Depending on registration and waiting time, expect to spend between 30 to 90 minutes at the testing site.
Location
If your oncologist recommends a CA 27.29 test, the blood draw can often be done in the healthcare provider’s office during your visit. You may also be referred to a nearby lab.
What to Wear
When going to your test, wear a top that is either short-sleeved or has sleeves that can easily be rolled up. Some people prefer wearing long sleeves so that they can cover the bandage or puncture mark after the test.
Food and Drink
There are no food or drink restrictions for the CA 27.29 test.
Medications
You should tell the phlebotomist (the medical professional drawing blood) if you are taking Herceptin (trastuzumab) or any other monoclonal antibodies derived from mouse antigens because they can affect your results. If you are unsure whether a drug you’re taking might alter your CA 27.29 test, speak with your oncologist.
Cost and Health Insurance
The cost of a CA 27.29 test can vary by location and lab, and it generally runs about $70. Your health insurance will usually cover some or all the cost if you have metastatic breast cancer. This may not be true if the test is used for screening purposes.
Speak with your insurance company to confirm what your co-pay or coinsurance costs will be in advance of the test. You should also check that the lab used is an in-network provider, or you may find yourself having to pay the full price.
If you don’t have insurance and must pay out of pocket, you can shop around for the best price. You should also ask your oncologist for information regarding financial assistance programs that can help pay for your ongoing treatment and care.
What to Bring
Be sure to bring a method of identification, your health insurance card, and a form of payment to cover any copay, coinsurance, or out-of-pocket costs.
During the Test
When you arrive for the test, you will need to check in, complete a registration form, and make payment for any out-of-pocket costs. A consent form may be provided.
A phlebotomist will perform the blood draw.
Pre-Test
You will be led to a room and seated in a chair. The phlebotomist will ask which arm you prefer the blood drawn from. Some people suggest the arm you don’t write with; others recommend the arm with the most prominent veins.
After placing an elastic tourniquet around your upper arm, the phlebotomist will swab the puncture site (typically the crook of the arm) with an alcohol swab.
Throughout the Test
You will feel a tiny prick as the needle is inserted into your vein.
For the CA 27.29 test, a full test tube of blood (minimum of 3 milliliters) is needed. The vacuum-sealed tube will usually have a gold or red rubber cap.
Once completed, the needle will be withdrawn and a cotton ball or gauze will be placed on the puncture site until the bleeding stops (usually within a minute). The phlebotomist will then put an adhesive bandage over the wound.
Post-Test
You should be able to leave shortly after your test is completed as long as you are not bleeding or feeling dizzy. After that, you can continue with your day without limitations.
After the Test
After the test, it is not uncommon to feel mild soreness at the puncture site for the first couple of hours. Redness or bruising may also occur. Once the bleeding is fully stopped, you can remove the adhesive bandage. However, if the puncture wound is visible, you need to keep it covered to prevent infection.
Although infection is rare, it can sometimes occur. Call your healthcare provider if you experience continuing or worsening pain in your arm or hand, develop a high fever, or have persistent bleeding after the blood draw.
Interpreting Results
The results of your blood test should be available within three to five working days. The report will include a reference range, outlining levels of the CA 27.29 antigen that are considered normal or abnormal. The reference range is based on the expected values in a population of people.
While the CA 27.29 reference range can vary slightly from one lab to the next, it is generally accepted that anything less than 38.6 units per millimeter (U/mL) is normal. A normal result generally indicates that you don’t have an active cancer.
A CA 27-29 value higher than 38.6 U/mL can indicate one of the following:
You have active cancer. Cancer may be spreading. Cancer may be recurring. You have another cancerous or noncancerous condition. You have been exposed to mouse-derived antibodies.
If the CA 27.29 test is used to monitor your response to treatment, a single value is less important than how the results trend over time. Decreasing values are an indication that a treatment is working, while increasing or stagnating values may suggest that treatment is not working.
False Positives
Aside from the recent start of cancer treatment, there are other things that pose a risk of a false-positive result. A sudden rise in CA 27.29 levels may occur for reasons other than breast cancer, be them benign or cancerous.
Such conditions include:
Acute hepatitis (inflammation of the liver) Benign (noncancerous) breast cysts Colon cancer Kidney disease Liver cancer Cirrhosis (late-stage scarring of the liver) Lung cancer Pelvic inflammatory disease (PID, infection of the upper female reproductive organs) Ovarian cancer Ovarian cysts Pancreatic cancer Prostate cancer
Follow-Up
If your CA 27.29 results are abnormally elevated, your oncologist will likely order additional tests to determine the cause.
These may include:
A repeat of the CA 27. 29 test Imaging tests, such as an ultrasound, computed tomography (CT), positron-emission tomography (PET), or bone scan Tumor marker tests to check for other cancers, such as the CA 125 antigen for ovarian cancer or the alpha-fetoprotein for liver cancer CellSearch circulating tumor cell (CTC) test, a newer assay used to monitor metastatic breast, colorectal, and prostate cancer Liver function tests to check for liver disease Blood tests to check for viral hepatitis Biopsy, if suspicious growths are found
Summary
The CA 27.29 blood test can help your doctor monitor your cancer and its response to treatment. Taken together with other tools and clinical monitoring, this is a helpful test to have. It is mostly noninvasive with minimal pain and adds to the larger clinical picture. While it is not helpful for diagnosis or staging, it can be used in other ways.
A Word From Verywell
The CA 27.29 test is an important tool for monitoring the treatment and care of metastatic breast cancer. The test can be used to monitor your response to treatment and/or assess whether cancer is active or spreading, but it has its limitations. Even if a value is high, you should not assume that cancer is the cause. The CA 27.29 is only useful when used in combination with other tests.
If you are worried about your results or have concerns about your CA 27.29 numbers, talk with your doctor. Cancer is not the only thing that can increase this tumor marker, and your doctor is using this test as part of the bigger picture.
https://stanfordhealthcare.org/medical-tests/t/tumor-markers/types/ca-27-29.html
