CA 15-3 Test


The CA 15-3 test is a blood test that measures the level of CA 15-3 protein in the blood. CA 15-3 is a protein produced by cells in response to changes occurring in the body, and it is considered a tumor marker because high levels of the antigen may indicate certain cancers, including breast cancer

However, it is important to note that CA 15-3 tests are not used to diagnose cancer, but rather to assess how cancer is responding to treatment

Uses of the CA 15-3 Tumor Marker Test

The CA 15-3 tumor marker test is used to monitor response to breast cancer treatment and disease recurrence

Several studies have shown that an increase in CA 15-3 levels may predict recurrence approximately 5–6 months prior to the onset of signs or symptoms, or positivity of other tests

Interpreting the Results

CA 15-3 levels are higher than normal in most women with breast cancer that has spread to other parts of the body (called metastatic breast cancer). However, not all types of breast cancer will cause CA 15-3 levels to rise, as some types of cancer cells don’t over-produce the antigen

It is important to note that having a positive CA 15-3 blood test does not mean you have breast cancer or that your breast cancer has come back. Other conditions can cause CA 15-3 to be in your blood. Noncancerous conditions of the breast, ovary, and liver can also cause CA 15-3 to go up
The results of this test are evaluated with other clinical information. In general, increasing values may be a sign of disease progression or recurrence, while decreasing values may mean disease regression


The CA 15-3 tumor marker test is an important tool for monitoring response to breast cancer treatment and disease recurrence. At our laboratory, we offer accurate and reliable CA 15-3 tests to aid in the diagnosis and management of breast cancer. Contact us today to learn more about our CA 15-3 test and how we can assist in your cancer care.

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