Patients and Caregivers

Breast Cancer


Breast cancer is the most common cancer diagnosed in women. More than 1 million women worldwide are diagnosed with breast cancer each year. The American Cancer Society estimates 178,000 women in the U.S. will be diagnosed with invasive breast cancer resulting in approximately 40,000 deaths. With the use of mammography as a screening tool and better treatment for breast cancer the death rates from breast cancer are steadily decreasing.1

Breast cancer is a malignant tumor that starts in the cells of the breast. There are many different forms of breast cancer, some that are invasive (meaning that it has spread to other portions of the breast tissue) and those that are non-invasive. The two most common types of breast cancer are: Ductal carcinoma in situ, the most common form of non-invasive breast cancer; and Invasive ductal carcinoma.

CA 15-3® and CA27.29 are biomarkers that are highly associated with breast cancer and are derived from the MUC1 gene. Neither of these markers is recommended by physician organizations for use in the screening or detection of breast cancer. This is in part due to the elevation of the markers in benign conditions including: breast, liver and kidney disorders and other cancers.

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Diagnosis of Breast Cancer

Breast cancer today is often diagnosed through mammography or the identification of a lump within the breast. Following imaging and a clinical breast exam that is suggestive of cancer patients will often be referred to a specialist for a biopsy. The biopsy results are then used to diagnose the type of cancer.

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Management of Breast Cancer

Upon diagnosis of breast cancer there are many options available to women for treatment, which include: surgery, chemotherapy, radiation, hormone therapy, and biological therapy. Patients can receive one treatment but many women will receive a combination of therapies. The therapy that is recommended for patients is dependant upon the stage of disease at time of diagnosis and surgery.

CA 15-3 and CA27.29 are used in combination with other testing to aid physicians in following the course of cancer in patients. They have been approved for monitoring the response to therapy and to monitor for recurrence of disease in patients diagnosed with breast cancer.

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Frequently Asked Questions

What is the CA 15-3 tumor marker and how does it relate to breast cancer?

CA 15-3 is a tumor marker that is elevated in the serum/plasma of approximately 75% of women with metastasized breast cancer. CA 15-3 levels can also be raised due to the presence of other conditions or cancers (for example, colorectal cancer, hepatitis, and benign breast disease).

How is the CA 15-3 test performed?

A blood sample is taken from the patient and then sent to a laboratory for testing to determine the level of CA 15-3 present in the blood. The laboratory determines the amount of antigen present in the blood sample by using a monoclonal antibody known to specifically bind to the CA 15-3 antigen. By measuring the amount of bound antigen/antibody units the laboratory can quantitate the amount of CA 15-3 antigen present in the patient's blood sample.

Why is the CA 15-3 test performed?

The CA 15-3 test is performed to aid physicians in the monitoring of treatment of women with invasive breast malignancies. It can also be used to diagnose recurrence of the disease following first-line therapy. By using the measurements obtained from the CA 15-3 test the physicians can help to determine if the patient is responding to treatment or if additional treatment or testing is required.

What do the CA 15-3 test results mean?

Physicians use the CA 15-3 test results in conjunction with other diagnostic test results and full medical history to make decisions about the management of their patients. A physician typically requests a CA 15-3 test prior to the patient receiving treatments. This result serves as a baseline to compare with future measurements. During therapy, serial CA 15-3 results may be used to monitor response to therapy. Increasing results may be indicative of progressive disease, decreasing results may be indicative of response to therapy and constant results may be associated with stable disease.

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If you'd like to learn more, please refer to one of our recommended breast cancer resources.

  • CDC's National Breast Cancer Early Detection Program - Through their national breast cancer early detection program, CDC's mission is to provide critical screening services to underserved women in the United States.
  • Living Beyond Breast Cancer - The mission of Living Beyond Breast Cancer is to empower all women affected by breast cancer to live as long as possible with the best quality of life.
  • Susan G. Komen Breast Cancer Foundation - For more than 20 years, the Susan G. Komen Breast Cancer Foundation has been a leader through its efforts to eradicate breast cancer through research, education, screening, and treatment.

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  1. Ferlay, J, Bray, F, Psiani, P, Parkin, DM. Cancer Incidence, Mortality and Prevalence Worldwide IARC CancerBase No.5, version 2.0 Lyon, France: IARCH Press; 2004.