CA 15-3 (Cancer Antigen 15-3) – Serum Test

Overview:
CA 15-3 is a tumor marker primarily used in monitoring breast cancer. It is a protein antigen found on the surface of certain cancer cells and released into the bloodstream. Elevated levels of CA 15-3 can indicate the presence or progression of breast cancer, though it may also be increased in other malignancies or benign conditions.

Sample Type:
Serum (blood sample collected and processed to obtain the liquid portion without cells).

Purpose:

To monitor the treatment response in patients diagnosed with breast cancer.

To detect recurrence or metastasis after initial therapy.

Not recommended as a screening tool for breast cancer due to lack of specificity and sensitivity.

How It Works:
CA 15-3 is measured by immunoassay techniques that detect the antigen concentration in the serum. Normal levels vary depending on the laboratory but generally fall below 30 U/mL.

Clinical Significance:

Elevated CA 15-3 levels often correlate with tumor burden and disease progression in breast cancer patients.

Rising levels during follow-up may signal recurrence or metastasis.

Can be used alongside other diagnostic methods like imaging and clinical evaluation.

May also be elevated in other cancers such as ovarian, lung, and liver, or in benign conditions like liver disease, benign breast disease, and inflammation.

Limitations:

Not a definitive diagnostic test for cancer.

Elevated levels can be caused by non-cancerous conditions.

Should be interpreted within the broader clinical context.