At a Glance
Why Get Tested?
To monitor the response to treatment of breast cancer and to watch for recurrence of the disease
When to Get Tested?
When you have been or are being treated for breast cancer
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
Cancer antigen 15-3 (CA 15-3) is a normal product of breast cells. Levels of CA 15-3 are often increased in breast cancer. CA 15-3 does not cause cancer; rather, it is a protein that is shed by the tumour cells, making it useful as a marker to follow the course of the cancer.
CA 15-3 is elevated in about 30% of women with localised breast cancer and in about 75% of those with breast cancer that has metastasised (spread to other organs). CA 15-3 also may be elevated in healthy people and in individuals with other cancers, or diseases, such as bowel cancer, lung cancer, cirrhosis, hepatitis, and benign breast disease.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.