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CA 15-3

CA 15-3

Test Highlight

CA 15-3


Clinical Use

  • Therapeutic monitoring of patients with metastatic breast cancer

  • Early detection of recurrent breast cancer

Clinical Background

Both CA 15-3 and CA 27.29 have received FDA approval for monitoring patients with advanced breast cancer. In such patients, the American Society of Clinical Oncology (ASCO) guidelines recommend monitoring these tumor markers in conjunction with imaging and clinical examination (J Clin Oncol. 2007;25:5287-5312). Monitoring CA 15-3 or CA 27.29 can be especially useful to detect treatment failure in the absence of readily measurable disease.


Chemiluminescent microparticle 2-step sandwich immunoassay

Interpretive Information

Normal values for CA 15-3 are <32 U/mL. CA 15-3 levels are increased in less than 50% of patients with early-stage breast cancer, substantially limiting the usefulness in that population. However, in more advanced disease, a rising CA 15-3 level may have clinical utility (Clin Chem. 2002;48:1151-1159). Confirmed increases of ≥25% have been suggested to be clinically significant.

Values obtained with different assay methods or kits cannot be used interchangeably. CA 15-3 levels, regardless of value, should not be interpreted as absolute evidence of the presence or absence of disease.

Content reviewed 12/2012

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