At a Glance
Why Get Tested?
To monitor the response to treatment of invasive breast cancer and to help watch for recurrence of the disease
When to Get Tested?
When you have been or are being treated for invasive 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 protein that is produced by normal breast cells. In many people with cancerous breast tumors, there is an increased production of CA 15-3 and the related cancer antigen 27.29. CA 15-3 does not cause cancer; rather, it is shed by the tumor cells and enters the bloodstream, making it useful as a tumor marker to follow the course of the cancer.
CA 15-3 is elevated in only about 10% of women with early localized breast cancer but is elevated in about 80% of those with metastatic breast cancer.
CA 15-3 may also be elevated in healthy people and in individuals with other cancers (e.g., colon, lung, pancreas, ovary, or prostate malignancies) or certain conditions (e.g., 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.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
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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.
Sources Used in Current Review
(Revised 2012 October 18). Tumor Markers. American Cancer Society [On-line information]. PDF available for download at http://www.cancer.org/acs/groups/cid/documents/webcontent/003189-pdf.pdf through http://www.cancer.org. Accessed October 2012.
Thaker, N. et. al. (Updated 2012 May 24). CA 15-3. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2087491-overview#showall through http://emedicine.medscape.com. Accessed October 2012.
(© 1995-2012). Cancer Antigen 15-3 (CA 15-3), Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/81607 through http://www.mayomedicallaboratories.com. Accessed October 2012.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 206-207.
Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 496, 500.
Pagana and Pagana. Mosby's Manual of Diagnostic and Laboratory Tests. Fourth Edition. Pg 142.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Check, W. (1998 July) Reaching agreement on tumor markers. CAP Today, In the News [On-line journal]. Available online at http://www.cap.org/captoday/archive/1998/julycover.html through http://www.cap.org.
NCI (1998 April 27). Tumor markers. National Cancer Institute, Cancer Facts [On-line information]. Available online at http://cis.nci.nih.gov/fact/5_18.htm through http://cis.nci.nih.gov.
ACS (2000 July 19). Tumor Markers. American Cancer Society, Prevention and Early Detection [On-line information]. Available online through http://www.cancer.org.
AACC (2001 July 27) Use of Tumor Markers in Cancer Patients Leads to Better Detection, Decreasing Mortality. AACC Media Center, American Association for Clinical Chemistry [On-line press release]. PDF available for download at http://www.aacc.org/media/TumorMarkers.pdf through http://www.aacc.org.
ASCO (1996 May 17, adopted, revision every 3 years). CA 15-3 as a Marker for Breast Cancer. American Society for Clinical Oncologists, Clinical Practice Guidelines for the Use of Tumor Markers in Breast and Colorectal Cancer [On-line guidelines]. Available online at http://www.asco.org/prof/pp/html/guide/tumor/m_tumor10.htm through http://www.asco.org.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 214-215.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 247.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 206-207.
(Revised 2008 December 08). Tumor Markers. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/PED/content/PED_2_3X_Tumor_Markers.asp?sitearea=PED through http://www.cancer.org. Accessed August 2009.
(Updated 2009 May) Tumor Markers. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/resources/print/TumorMarkers.pdf through http://www.arupconsult.com. Accessed August 2009.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006, Pp 770-771.
Park, B et al. Preoperative CA 15-3 and CEA serum levels as predictor for breast cancer outcomes. Annals of Oncology 2008 19(4):675-681. Available online at http://annonc.oxfordjournals.org/cgi/content/full/19/4/675 through http://annonc.oxfordjournals.org. Accessed September 2009.
Merck (2000). Cancer and the Immune System. The Merck Manual of Medical Information Home Edition, Section 15 Cancer, Ch 163 [On-line information]. Available online at http://www.merck.com/pubs/mmanual_home/sec15/163.htm through http://www.merck.com.
Duffy, M. (1999). CA 15-3 and related mucins as circulating markers in breast cancer. Ann Clin Biochem [On-line journal]. Vol 36: 579-586. PDF available for download at http://www.leeds.ac.uk/acb/annals/annals_pdf/Sept%2099/ACB579.PDF through http://www.leeds.ac.uk.
Srirangam, S. and Harland, R. (2001). Management of Advanced Breast Cancer. Forum for Registrars In Surgical Training [On-line information]. PDF available for download at http://www.frist.org/asit/meetings/yearbook2001/BREAST%20CANCER.pdf through http://www.frist.org.