CA 15-3

Test Description

A tumor marker is a substance produced by body cells in response to the presence

of cancer. Cancer antigen 15-3 (CA 15-3) is a glycoprotein that has been found in

benign and malignant disease of the breast, as well as breast carcinoma that has

metastasized to the liver or bone. Highest CA 15-3 values are found in metastatic

breast disease. Testing for CA 15-3 is useful in the diagnosis of metastatic breast

cancer and for the monitoring of patient response to breast cancer treatment.

Because CA 15-3 values may not increase in early malignancy of the breast, it is

not useful as a screening test. Elevated CA 15-3 levels have also been found in

patients without cancer and in patients with other cancers such as liver, lung, and

ovarian cancer.

The higher the CA 15-3 level, the more advanced the breast cancer and greater

likelihood of metastasis. Mild to moderate elevation of this marker can also be seen

in some noncancerous conditions, such as cirrhosis.

THE EVIDENCE FOR PRACTICE

According to the American Society of Clinical Oncology, present data are insufficient to

recommend CA 15-3 or CA 27.29 for screening, diagnosis, staging, or surveillance following

primary treatment.

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Normal Values :<22 U/mL (<22 kU/L SI units)

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Possible Meanings of Abnormal Values

Increased

Breast cancer

Chronic hepatitis

Cirrhosis

Colorectal cancer

Fibrocystic breast disease

Liver cancer

Lung cancer

Metastatic breast cancer

Ovarian cancer

Pancreatic cancer

Sarcoidosis

Systemic lupus erythematosus

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Interventions/Implications

Pretest

• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.

• No fasting is required before the test.

Procedure

• A 5-mL blood sample is collected in a red-top tube.

• Gloves are worn throughout the procedure.

Posttest

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• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued

  bleeding.

• The sample is labeled and transported to the laboratory.

• Report abnormal findings to the primary care provider.

 Clinical Alerts          

• CA 15-3 levels in noncancerous conditions have a tendency to remain stable over

time, whereas in metastatic breast cancer, the levels continue to rise.

• Normal CA 15-3 values may occur early in breast cancer.