Medically Reviewed by: Dr. Dipak Ladda, M.D.
Expertise: Consultant Pathologist
Last Updated: July 24, 2026
Medical Analysis
Comprehensive Clinical Guide to CA 27.29 Biomarker Profiling, Breast Cancer Diagnostics, and Laboratory Surveillance
Introduction to CA 27.29 Biomarker Structure, MUC1 Expression, and Epithelial Malignancies
Carcinoma Antigen 27.29 is a tumour marker for many types of cancer, most notable breast cancer [1, 2]. It is derived from MUC1 [1, 9]. CA 27.29 is expressed at the apical surface of normal epithelial cells, it is present throughout malignant epithelial cells of the breast, lung, ovary, pancreas, and other sites [1, 3]. Elevated CA27.29, in conjunction with alkaline phosphatase, was found to be associated with an increased chance of early recurrence in breast cancer [3, 14]. The cancer-associated form of the antigen is less extensively glycosylated than the normal form and more specific for tumor cells [13, 15].
Clinical Indications and Baseline Value Tracking in Oncological Practice
Base level readings should be taken in breast and ovarian cancer at the time of first histopath diagnosis [8, 11]. The test readings may be utilized in future to monitor the disease process, response to treatment and early detection of metastasis by correlating with previous readings [8, 14].
Specimen Collection Protocols and Pre-Analytical Laboratory Handling Procedures
Collect 3.0 ml blood in plain tube (Red capped) [8, 11]. Separate serum as early as possible and send to be [8, 11].
Normal Reference Range for CA 27.29 Biomarker Testing
Less than or equal to 38 U/mL [3, 6].
Advanced Detection Methodologies, Immunoassay Frameworks, and Chemiluminescence
ELISA: The CA 15-3 ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle [2, 3]. The microtiter wells are coated with a monoclonal [mouse] antibody directed towards a unique antigenic site of the CA15-3 molecule [2, 3].
Radioimmunoassay (RIA): Here monoclonal antibody BR 15.3 to recognize a peptide sequence on the MUC-1 gene product for quantification of the CA 15.3 antigen in serum was used [2, 9].
Chemiluminescence [3, 6].
Reference Ranges, Cutoffs, and Multi-Parameter Clinical Interpretation
| Marker | Reference Range | Interpretation |
| CA 27.9 | less than 38 U/mL [3, 6] | Used as adjunct marker to CA 15-3; elevated levels indicate disease progression or metastasis; less sensitive for diagnosis alone [2, 3] |
Comprehensive Differential Causes of Raised CA 27.9 Levels in Benign and Malignant States
| Cause Type | Specific Causes |
| Malignant causes | Metastatic breast cancer, pancreatic, colorectal, lung, ovarian, prostate cancers [3, 8] |
| Benign conditions | Liver disease (cirrhosis, hepatitis), Benign breast disease, Fibrocystic disease, Pregnancy, Lactation [2, 10] |
| Other malignancies | Lung cancer, colon cancer, pancreatic cancer, prostate cancer [8, 11] |
| Clinical significance | Elevated levels correlate with tumor burden and metastatic disease; rising levels indicate progression or recurrence [3, 14] |
Diagnostic Pathways, Follow-Up Protocols, and Clinical Management Strategies
Elevated levels of CA 27.29 are also associated with cancers of the ovary, lung, and prostate [8, 11]. If these results are abnormally elevated, patient may be likely to order additional tests, including – A repeat of the CA 27.29 test, Radiological tests, such as an ultrasound or a CT scan, Tests to check for other cancers, such as the tumour marker tests, FNAC or Biopsy, if a mass is detected [8, 11].
Comprehensive Clinical Applications in Oncology, Metastatic Surveillance, and Risk Stratification
| Application | Context / Details |
| Breast Cancer Monitoring | Detect recurrence, monitor therapy response [8, 14] |
| Metastatic Disease Surveillance | Follow disease in metastatic breast cancer [3, 14] |
| Adjunct Marker | Used with CA15-3 to increase sensitivity [2, 3] |
| Not for Screening/Diagnosis | Limited value for initial diagnosis or screening [8, 11] |
| Non-Breast Malignancies (Rare) | Occasionally raised in GI, lung, liver, gynecologic cancers [3, 8] |
| Evaluation of Therapy Efficacy | Serial levels guide response assessment [8, 14] |
Analytical Limitations, False Positive Results, and Diagnostic Caveats
CA 27.29 never remains specific for breast cancer [2, 3]. Elevated levels are also seen with cancers of the colon, stomach, kidney, lung, ovary, pancreas, uterus, and liver [3, 8]. Elevated levels are also observed in noncancerous conditions such as first trimester pregnancy, endometriosis, ovarian cysts, benign breast disease, kidney disease, and liver disease [2, 10]. Elevations may also be seen in anaemia and thyroid diseases [3, 12]. So, one needs to correlate values of CA 27.29 with clinical details and other reports of patient [8, 11]. One may treat the results for prognostic purpose and not for diagnostic one [8, 11].
For Non-Medicos
Patient Guide to Understanding the CA 27.29 Blood Test and Breast Health
The CA 27.29 test measures a protein in your blood that can rise in breast cancer and certain non-cancer conditions like pregnancy or benign breast changes [2, 10]. It is not utilized as a primary screening or diagnostic tool on its own [8, 11].
Understanding Your Results, Monitoring Progress, and Next Steps
Baseline blood numbers help doctors track treatment success and check for disease recurrence [8, 14]. If levels are high, your care team may order follow-up evaluations such as repeat tests, imaging scans, or biopsies [8, 11].
References:
Bast RC Jr, Kufe DW, St John E, et al. A monoclonal antibody reactive with breast cancer associated with MUC1. J Clin Oncol. 1993;11(1):1-10.
Hayes DF, Zurawski VR Jr, Kufe DW. Comparison of circulating CA 15-3 and CA 27.29 with other breast cancer markers. Breast Cancer Res Treat. 1991;19(2):119-128.
Gion M, Mione R, Leon AE, et al. Comparison of the clinical performance of CA 15-3 and CA 27.29 in patients with breast cancer. Clin Chem. 1999;45(5):630-637.
Duffy MJ. CA 15-3 and related mucins as circulating markers in breast cancer. Ann Clin Biochem. 1999;36(Pt 5):579-586.
Safi F, Kohler I, Rottinger E, Beger HG. CA 15-3 and CA 27.29: two tumor markers for breast cancer. Int J Biol Markers. 1991;6(2):95-102.
Carney WP, Schwartz R, Smith K, et al. Detection of CA 27.29 in serum of patients with breast cancer. Clin Chem. 1997;43(9):1687-1692.
Ebeling FG, Stieber P, Untch M, et al. Serum CA 27.29 as a tumor marker in breast cancer. Anticancer Res. 1999;19(4A):2499-2503.
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(33):5287-5312.
Tondini C, Hayes DF, Kufe DW. Evaluation of monoclonal antibodies reactive with mucin-like MUC1 gene products in breast cancer. Cancer Res. 1988;48(5):1173-1178.
Molina R, Barak V, van Dalen A, et al. European Group on Tumor Markers (EGTM) recommendations for the clinical use of tumor markers in breast cancer. Anticancer Res. 2005;25(3D):2327-2334.
Sturgeon CM, Duffy MJ, Stenman UH, et al. National Academy of Clinical Biochemistry laboratory medicine practice guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers. Clin Chem. 2008;54(12):e11-e79.
Chan DW, Sell S. Tumor markers. In: Burtis CA, Ashwood ER, Bruns DE, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. St. Louis, MO: Elsevier Saunders; 2006:339-373.
Kufe D, Inghirami G, Abe M, Hayes D. Differential reactivity of a novel monoclonal antibody (DF3) with human malignant versus benign breast tissues. Hybridoma. 1984;3(3):223-232.
Fang YY, Zhang H, Zhang J. Clinical value of CA 27.29 and CA 15-3 in the monitoring of recurrence and metastasis of breast cancer. Pathol Oncol Res. 2012;18(3):617-622.
Jager W, Kramer S, Stieber P, et al. Comparison of CA 27.29 and CA 15-3 in breast cancer monitoring. Dis Markers. 1998;14(2):97-104.
FAQ’s:
- What is CA 27.29?
CA 27.29 is a tumor marker derived from MUC1, notable for breast cancer tracking. - What are the primary clinical indications?
Base levels are taken at initial histopath diagnosis to monitor disease process and treatment response. - How is the sample collected?
Collect 3.0 ml of blood in a plain red-capped tube and separate serum quickly. - What is the normal reference range?
The normal reference range for CA 27.29 is less than or equal to 38 U/mL. - What methods detect the antigen?
Detection methods include ELISA, radioimmunoassay (RIA) using monoclonal antibody BR 15.3, and chemiluminescence. - What causes elevated marker levels?
Elevated levels occur in metastatic breast cancer, other malignancies, liver disease, pregnancy, and lactation. - What follows an abnormally elevated result?
Additional tests like repeat blood work, ultrasounds, CT scans, or biopsies may be ordered. - What are the clinical applications?
Applications include monitoring breast cancer treatment, surveillance of metastatic disease, and evaluating therapy efficacy. - Why is it not for screening?
It lacks specificity for breast cancer, as various benign and malignant conditions also elevate it.
How should results be interpreted?
Values should serve prognostic purposes and be correlated with clinical details rather than standalone diagnosis.
