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CA15-3

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Last Modified: June 18, 2009

Dear OncoLink "Ask The Experts,"
What is the significance of CA15-3 in the management of metastatic breast cancer? 

CA 15-3 and CA 27-29 are simply chemical names for particular cellular surface antigens. They are only important because they are shed into the bloodstream by cancer cells and are convenient markers in tracking the progress of someone getting treatment for metastatic cancer. The amount of CA 15-3 in the blood should go down if the treatment is effective. We usually measure the value at one-or-two month intervals in someone on treatment for metastatic breast cancer. When starting a new treatment, it can take a few months to see a decrease, so we may wait longer to recheck the levels when therapy is changed.

Although these values are recommended for use in following and evaluating metastatic cancer treatment, they have not shown any value in screening, diagnosis, staging or monitoring for recurrence after surgery or adjuvant therapy.