What are the primary tumor markers used for breast cancer?

From the Guidelines

The primary tumor markers used for breast cancer include CA 15-3, CA 27.29, and carcinoembryonic antigen (CEA), which are primarily used to monitor treatment response and detect recurrence in patients with advanced breast cancer, rather than for initial diagnosis. These markers are used in conjunction with diagnostic imaging, history, and physical examination to contribute to decisions regarding therapy for metastatic breast cancer 1. CA 15-3 and CA 27.29 are the most commonly used markers, as they measure the same antigen (MUC1) found on breast cancer cells, with elevated levels potentially indicating tumor growth or recurrence. CEA is less specific but may be used alongside other markers.

• The use of CA 15-3, CA 27.29, and CEA as adjunctive assessments to contribute to decisions regarding therapy for metastatic breast cancer is based on clinical experience and informal consensus, with moderate strength of recommendation 1.
• Additionally, while not traditional tumor markers, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status are crucial biomarkers that guide treatment decisions, with HER2 expression and/or amplification evaluated in every primary invasive breast cancer to guide selection of trastuzumab in the adjuvant and/or metastatic setting 1.
• It's essential to note that tumor markers have limitations in sensitivity and specificity, so they should be interpreted alongside clinical findings, imaging studies, and other diagnostic tests rather than used in isolation.
• The American Society of Clinical Oncology (ASCO) believes that cancer clinical trials are vital to inform medical decisions and improve cancer care, and that all patients should have the opportunity to participate 1.

From the Research

Tumor Markers for Breast Cancer

• The primary tumor markers used for breast cancer include CA 15-3, BR 27.29 (CA27.29), carcinoembryonic antigen (CEA), tissue polypeptide antigen, tissue polypeptide specific antigen, and HER-2 (the extracellular domain) 2.
• CA 15-3 is the most widely used serum tumor marker in follow-up and detection of breast cancer recurrence 3, 4.
• Elevated preoperative CA 15-3 levels are associated with poor prognosis in both early and late stage disease 3.
• CA 15-3 is particularly valuable for treatment monitoring in patients that have disease that cannot be evaluated using existing radiological procedures 5.

Clinical Applications of CA 15-3

• The main use of CA 15-3 is for monitoring therapy in patients with metastatic disease 5.
• CA 15-3 may also be used in the postoperative surveillance of asymptomatic women who have undergone surgery for invasive breast cancer 5.
• Serial determination of CA 15-3 can provide median lead-times of 5-6 months in the early detection of recurrent/metastatic breast cancer 5.
• Higher levels of CA 15-3 are associated with advanced stages and recurrence, and may be a reliable prognostic marker 6.

Limitations of CA 15-3

• The main limitation of CA 15-3 as a marker for breast cancer is that serum levels are rarely increased in patients with early or localized disease 2, 5.
• CA 15-3 should not be used alone for monitoring therapy, but measured in conjunction with diagnostic imaging, clinical history, and physical examination 5.