Cancer Antigen 15-3 (CA 15-3)


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Subject: Cancer Antigen 15-3 (CA 15-3)

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  • This glycoprotein is a mucinous carbohydrate antigen product of the MUC1 gene expressed on various adenocarcinomas, especially breast. It is a high molecular weight (300–450 kDa) 1 polymorphic epithelial mucin.

  • Normal value: <38 U/mL.


  • Marker for breast carcinoma. United States Food and Drug Administration (USFDA) approval is only for detection of breast carcinoma recurrence before symptoms and to monitor response to treatment. Significant change is ±25%.

  • Not approved for screening, although increased values may occur ≤9 months before clinical evidence of disease.


Increased In

  • Approximately 80% metastatic breast cancer

  • Pancreas, lung, ovarian, colorectal, and liver cancers with less specificity


  • CA 15-3 should not be used to diagnose breast cancer.

  • Clinical sensitivity is 0.60, the specificity is 0.87, and the PPV is 0.91.

  • It is considered equivalent to cancer antigen 27.29 mucin marker.

Suggested Reading

Duffy  MJ, Duggan  C, Keane  R High preoperative CA 15-3 concentrations predict adverse outcome in node-negative and node-positive breast cancer: study of 600 patients with histologically confirmed breast cancer. Clin Chem.  2004;50:559–563.