Breast cancer is the most common form of cancer among women, and early detection of the disease can dramatically improve the chances of successful treatment. Diagnosis and monitoring of breast cancer is through routine screening involving mammograms, coupled with breast ultrasound and biopsy if needed. The use of a breast cancer tumor marker blood test in the screening, diagnosis and monitoring of breast cancer has been considered in order to improve detection and treatment of the disease.
What Are Breast Cancer Tumor Markers?
Tumor markers are chemicals associated with the growth of malignant cells which can be detected in the blood. This allows for patient monitoring through a simple blood test, rather than more invasive procedures such as biopsy. A number of tumor markers exist, many of which have been associated with the development of breast cancer. Tumor markers recognized by the American Society of Oncology (ASCO) as having potential use in the diagnosis or management of breast cancer include CA 15-3, carcinoembryonic antigen (CEA), CA 27.29 and HER-2 ECD. However, the ASCO did not recommend any of these be used in the screening or diagnosis of patients free of detectable disease. The most widely studied breast cancer tumor markers are CA 15-3 and CEA.
Can a Tumor Marker Blood Test Be Used for Early Diagnosis?
The use of tumor markers in the early diagnosis of breast cancer is not generally recommended due to the lack of specificity and sensitivity of the tests in the early stages of the disease. For example, elevated CA 15-3 levels are present in less than 10% of patients with stage I disease, and elevated CA 15-3 may also be observed in healthy individuals, or patients with certain benign diseases. CEA has been observed to be elevated in only 26% of breast cancer patients.
Breast Cancer Tumor Marker Blood Test for Prognosis
There is some evidence to suggest that tumor markers such as CA 15-3 may have significant prognostic use in assessing patients diagnosed with the disease. For example, elevated pre-operative CA 15-3 has been correlated with both early relapse and death from the disease. Follow-up monitoring of tumor markers after surgery may also provide useful prognostic information.
Tumor Markers May Be Used in Monitoring
Some tumor markers such as CA 15-3 and serum HER-2 may be of use in predicting the response of a patient to particular types of therapy. Elevated HER-2 has been shown to indicate an increased likelihood of poor response to endocrine therapy, but is also associated with a good response to Herceptin combined with chemotherapy. Tumor markers may therefore be used to help determine the course of treatment to be used.
Tumor markers may also be used as a surveillance tool following primary treatment, or in the monitoring of response to therapy in advanced disease. CA 15-3 is considered to be the most effective tumor marker in these applications.
 “Diagnosing Breast Cancer" NHS Choices
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