From the Guidelines
Carcinoembryonic Antigen (CA) 27-29 should not be used for breast cancer screening or initial diagnosis due to its limited sensitivity and specificity, but it can be used as an adjunctive assessment to contribute to decisions regarding therapy for metastatic breast cancer, in conjunction with diagnostic imaging, history, and physical examination, as stated in the 2015 American Society of Clinical Oncology clinical practice guideline 1. The role of CA 27-29 in breast cancer management is primarily focused on monitoring disease recurrence in patients with previously treated disease. Some key points to consider when using CA 27-29 include:
- It is most valuable for detecting disease progression or recurrence during follow-up of patients with previously diagnosed breast cancer, particularly those with metastatic disease.
- The marker is typically measured through a simple blood test, with normal levels generally below 38 U/mL, though cutoff values may vary between laboratories.
- Rising CA 27-29 levels over time may indicate disease progression or recurrence, often preceding clinical or radiographic evidence by 2-9 months.
- However, interpretation requires caution as false positives can occur with benign conditions like liver disease, inflammatory disorders, and other cancers.
- CA 27-29 should always be used in conjunction with clinical assessment, imaging studies, and other diagnostic tools—never as a standalone test for making treatment decisions.
- The marker's utility lies in its ability to provide additional information when monitoring treatment response in metastatic breast cancer, potentially allowing earlier intervention when levels rise persistently, as supported by the 2007 American Society of Clinical Oncology update of recommendations for the use of tumor markers in breast cancer 1. It is essential to note that the use of CA 27-29 as a biomarker is based on clinical experience and informal consensus, with insufficient evidence to recommend its use alone for monitoring response to treatment, as stated in the 2015 American Society of Clinical Oncology clinical practice guideline 1.
From the Research
Role of CA 27-29 Marker in Breast Cancer Management
- The CA 27-29 marker is a soluble form of glycoprotein MUC1, which is overexpressed in tumors involving glandular epithelial cells, such as breast tumors 2.
- Measurement of CA 27-29 has been approved by the US Food and Drug Administration for monitoring disease activity in patients with breast cancer 2.
- The marker can be used to detect recurrent or metastatic disease, with lead times of approximately 2-9 months, although the clinical value of this lead time remains to be determined 2.
Clinical Value and Prognostic Significance
- Studies have shown that CA 27-29 is a valuable marker for breast cancer management, with comparable results to CA15.3 3.
- The marker has been shown to be more sensitive than CA15.3 to limited variations of tumor extension, although it cannot help clinicians in distinguishing stage I patients from stage II patients 3.
- Elevated CA 27-29 levels have been associated with larger tumor size, lobular histology, older age, and postmenopausal hormone status before the start of treatment 4.
Association with Circulating Tumor Cells
- Research has investigated the association between CA 27-29 and circulating tumor cells (CTCs) in patients with early-stage breast cancer 5.
- The study found that CTC and CA 27-29 positivity were significantly, but only weakly associated before chemotherapy and 5 years after chemotherapy, while no significant association was found immediately or 2 years after chemotherapy 5.
Limitations and Potential Confounding Factors
- False-positive results might be observed in certain patients with no evidence of malignant disease, such as benign breast disease, ovarian cysts, and liver disease 2.
- Potential confounding factors, such as nodal status, grading, hormonal status, and HER2/neu status, should be considered when interpreting tumor marker results 4.