Test Center

My Recent Searches

  • No Recent Search.

My Tests Viewed

  • No Test Viewed.

CA 27.29

CA 27.29

Test Summary

CA 27.29


Clinical Use

  • Therapeutic monitoring of patients with metastatic 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 monoclonal antibody used in the CA 15-3 assay1; therefore, both antibodies detect the same antigen. Elevated CA 27.29 levels are primarily associated with metastatic breast cancer, but may also be associated with primary breast or other malignant or nonmalignant conditions (Table).2,3

Table. Conditions That May Be Associated With Elevated CA 27.29 Levels2,3

Malignant Conditions

Nonmalignant Conditions

Metastatic breast cancer
Primary breast cancer
Ovarian cancer
Lung cancer
Pancreatic cancer
Colon cancer
Liver cancer

Acute hepatitis
Liver cirrhosis
Benign breast disorders
Benign liver disorders
Ovarian cysts

The American Society of Clinical Oncology (ASCO) guidelines support monitoring CA 27.29 levels in metastatic breast cancer patients with documented CA 27.29 elevation.4 CA 27.29 levels should be used in conjunction with imaging and clinical examination to guide therapeutic decisions.4 However, in the absence of readily measurable disease, CA 27.29 monitoring can be used to indicate treatment failure.4 ASCO does not recommend using CA 27.29 levels for screening or diagnosis of breast cancer5 or for routine surveillance of breast cancer patients after primary treatment.6

Individuals Suitable for Testing

  • Patients undergoing therapy for metastatic breast cancer


  • Competitive immunochemiluminometric assay

  • Analytical sensitivity: 8 U/mL

  • Reportable range: 8-90,000 U/mL

Interpretive Information

Rising CA 27.29 levels suggest lack of therapeutic response and/or progressive disease, whereas decreasing levels suggest response to treatment and disease regression. However, increasing CA 27.29 levels during the first 4 to 6 weeks of administration of a new therapy have been observed; therefore, rising levels during this interval should be interpreted with caution.4 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. Values obtained with different assay methods or kits cannot be used interchangeably.


  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. 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.

  3. Perkins GL, Slater ED, Sanders GK, et al. Serum tumor markers. Am Fam Physician. 2003;68:1075-1082.

  4. Van Poznak C, Somerfield MR, Bast RC, et al. Use of biomarkers to guide decisions on systemic therapy for women with metastatic breast cancer: American Society of Clinical Oncology clinical practice guideline. J Clin Oncol. 2015;33:2695-2704.

  5. 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.

  6. Khatcheressian JL, Hurley P, Bantug E, et al. Breast cancer follow-up and management after primary treatment: American Society of Clinical Oncology clinical practice guideline update. J Clin Oncol. 2013;31:961-965.

Content reviewed 05/2017

* The tests listed by specialist are a select group of tests offered. For a complete list of Quest Diagnostics tests, please refer to our Directory of Services.