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CA 27.29

CA 27.29

Test Summary

CA 27.29


Clinical Use

  • Therapeutic monitoring of patients with metastatic breast cancer

  • Early detection of recurrent breast cancer

Clinical Background

CA 27.29 is an epitope on the protein core of the MUC-1 mucin glycoprotein (a breast cancer associated antigen). This epitope is molecularly similar to the one recognized by the DF3 monoclonal antibody used in the CA 15-3 assay;1 therefore, both antibodies detect the same antigen. Elevated CA 27.29 levels are primarily associated with metastatic breast cancer. In a prospective study of 97 patients with metastatic breast cancer, 73% of patients with disease progression had a 20% or greater increase in CA 27.29 levels. Conversely, 71% of those without progression did not have a 20% increase in CA 27.29 levels.2 Additional studies further support the use of CA 27.29 levels for therapeutic monitoring.3,4

In another prospective study of 162 stage II and stage III breast cancer patients who were clinically free of disease at time of enrollment, CA 27.29 was positive in 60% of the patients who subsequently suffered a cancer recurrence (sensitivity = 60%). CA 27.29 was not elevated in 93% of the patients free of recurrence (specificity = 93%). Two consecutive positive CA 27.29 values were predictive of breast cancer recurrence 80% of the time and, conversely, a negative CA 27.29 value was predictive of the absence of a recurrence 91% of the time.2 Similar results had been obtained previously;5 consequently, CA 27.29 levels may be useful for predicting recurrent breast cancer.

CA 27.29 levels are not useful for screening or diagnosis of malignant disorders. This assay has received FDA approval for monitoring patients with advanced breast cancer. In such patients, the American Society of Clinical Oncology (ASCO) guidelines recommend monitoring this tumor marker in conjunction with imaging and clinical examination.6 CA 27.29 monitoring can be especially useful to detect treatment failure in the absence of readily measurable disease.

Patient Selection for Testing

  • Patients with a metastatic breast cancer diagnosis


  • Competitive immunochemiluminometric assay

  • Utilizes a mouse-monoclonal antibody (Mab B27.29) targeted toward the SAPDTRPA amino acid sequence on the MUC-1 molecule1

  • Analytical sensitivity: 3.5 U/mL

  • Analytical specificity: not affected by chemotherapeutic agents, therapeutic drugs, CEA, CA 125, CA 19-9, bilirubin, triglycerides, hemoglobin, or total protein

  • Aliases: BR, cancer antigen 27.29, breast cancer marker, breast carcinoma associated mucin antigen, and cancer associated breast antigen, ie, CABA

This test is performed using the Siemens (Bayer) Chemiluminescent method. Values obtained from different assay methods cannot be used interchangeably. CA 27.29 levels, regardless of value, should not be interpreted as absolute evidence of the presence or absence of disease.

Interpretive Information

Elevated CA 27.29 levels are associated with metastatic breast cancer and sometimes with primary breast cancer.5,7 CA 27.29 is also elevated in ovarian, liver, pancreatic and lung cancer, as well as in the nonmalignant conditions detailed in the table below. Rising levels suggest lack of therapeutic response and/or progressive disease, whereas decreasing levels suggest response to treatment and disease regression. CA 27.29 elevations in patients with a history of breast cancer and no clinical evidence of disease suggest recurrence.

Falsely elevated or depressed values may occur in samples obtained from patients who have received mouse monoclonal antibody preparations during diagnosis or therapy. Such patients may have developed human anti-mouse antibodies (HAMA) that interfere with accurate analysis. Levels within the normal range do not preclude the presence of cancer, nor are elevated results an absolute indication of malignancy. CA 27.29 test results should be interpreted in conjunction with other clinical and laboratory findings.

Distribution of CA 27.292,7


Number of Subjects

Percent (%) 39 U/mL

Apparently healthy women



Malignant Conditions  

Primary breast

 37  5

Metastatic breast

 97 81


 29  7


 43 26


 47 43


 45 47


 50 56


 20 55


 34 18




Nonmalignant Conditions

Benign breast

129  3


 49  2

Lactating women

 37 11


 25 24


 24  8

Chronic hepatitis

 48 10

Ovarian cyst

 50  6

Renal impairment

 20 15


  1. Reddish MA, Helbrecht N, Almeida A, et al. Epitope mapping of Mab B27.29 within the peptide core of the malignant breast carcinoma-associated mucin antigen coded for by the human MUC 1 gene. J Tumor Marker Oncol. 1992;7:19-27.

  2. CA 27.29 assay directional insert. Bayer Corporation, 2000.

  3. Abbate I, Correale M, Musci MD, et al. Monoclonal antibody B27.29 against mucinous breast cancer associated antigen CA 27.29 in breast cancer. Breast Cancer ResTreat. 1991;19:123.

  4. Dnistrain AM, Schwartz MK, Greenberg EJ, et al. Evaluation of a breast cancer antigen assayed on the Ciba Corning ACS:180 Automated Chemiluminescence System. J Tumor Marker Oncol. 1996;11:5-10.

  5. Chan DW, Beveridge RA, Muss H, et al. Use of Truquant BR radioimmunoassay for early detection of breast cancer recurrence in patients with stage II and stage III disease. J Clin Oncol. 1997;15:2322-2328.

  6. Harris L, Fritsche H, Mennel R, et al. American Society of Clinical Oncology 2007 update of recommendations for the use of tumor markers in breast cancer. J Clin Oncol. 2007;25:5287-5312.

  7. Bon GG, von Mensdorff-Pouilly S, Kenemans P, et al. Clinical and technical evaluation of ACS BR serum assay of MUC1 gene-derived glycoprotein in breast cancer, and comparison with CA 15-3 assays. Clin Chem. 1997;43:585-593.

Content reviewed 12/2012

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