Can You Detect Breast Cancer With a Blood Test?

Breast cancer is one of the most common cancers among women in the U.S. And there’s a lot of emphasis placed on the importance of routine screening and early detection. This is especially true because breast cancer often doesn’t cause symptoms in the beginning stages of disease. And the earlier someone is diagnosed, the easier it’s to treat and cure them. At this time, the mammogram is the best tool for breast cancer screening and detection. 

Can blood tests be used for screening?

There are currently no blood tests recommended for breast cancer screening. But researchers are studying some blood tests for this use. We’ll review two such blood tests here. 

Circulating tumor cells (CTCs) are cancer cells that have broken off from the original tumor and made their way into the bloodstream. But it’s unclear if testing for these cells is a good way to screen for breast cancer. A recent, small study of 28 women with recently diagnosed breast cancer found that CTCs were detectable in 3 out of 4 of these women. This means that 1 in 4 cases of breast cancer would’ve been missed if CTCs alone were used as a screening test in this group.  

But even if CTCs aren’t the best screening tool, they could play a different role in breast cancer diagnosis. Normally, when a person is diagnosed with breast cancer, they’ll get a simple biopsy procedure to collect a sample of cancer cells. This is done to learn more about the cancer cells. CTC blood tests may be valuable as a less invasive “liquid biopsy” after breast cancer has been diagnosed. This would allow people to avoid the biopsy procedure.

An antibody test is another blood test that researchers are studying as a possible screening tool. The immune system makes antibodies to help fight off foreign invaders, like bacteria or viruses. But the immune system also makes antibodies in response to cancer cells. An antibody blood test can detect breast cancer antibodies. Similar to CTCs, the antibody test isn’t yet ready for use as a screening tool. One recent study of women with breast cancer found that the antibody test was positive in less than half of the women. While further improvements are needed, a review of breast cancer antibodies predicts they could be used together with mammography as an effective screening tool.

Can blood tests be used to assess breast cancer risk?

While it’s still not clear if blood tests can be used to diagnose breast cancer, there are genetic blood tests that can help determine your risk for developing breast cancer in the future. Your provider may recommend these tests if you have a strong family history of breast cancer. You may also take these tests if you have a family member with a hereditary mutation in a gene that’s frequently associated with breast cancer (like BRCA1, BRCA2, or PALB2). This information can help you decide at what age you should start breast cancer screening, and how often you should get the screening done. 

What other blood tests are being used for breast cancer?

After breast cancer has been diagnosed, breast cancer staging is done to determine how advanced the cancer is. And there are quite a few blood tests that may be used in late-stage breast cancer. These are known as tumor marker tests. They detect proteins in the blood that tend to be higher when certain breast cancers are present. These tests can be used to help decide on a treatment plan and assess how a patient’s disease is responding to treatment. 

Examples of tumor markers include:

• HER2/neu protein: This protein tends to be higher in certain forms of cancer and can be used to guide treatment. If treatment is going well, the level of this protein should decrease.

• Cancer antigens 15-3 and 27-29: Normal breast cells produce these proteins, but levels tend to be higher in breast cancer and other types of cancer. These proteins can also be higher in people without cancer.

• Cancer antigen 125: This protein can be high in both ovarian and breast cancer.

• Carcinoembryonic antigen (CEA): This protein can be high in breast cancer and other types of cancer. A rising level of CEA may suggest disease spread or recurrence.  

• CTCs: As discussed above, CTCs may also be used in late-stage breast cancer. Similar to CEA, a rising CTC level may mean the cancer is progressing.

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Written by:

Fonda Jiang, MD

Dr. Fonda Jiang is a practicing allergist in Long Beach, California. At her current practice, Dr. Jiang is committed to working as a team with her adult and pediatric patients to diagnose and treat a wide range of allergic conditions.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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