CA 15.3 (Cancer antigen-Breast 15.3)

Clinical definition of the CA 15.3 test
Cancer antigen 15.3 (CA 15.3) is a protein that is produced by normal breast cells.  There is an increased production of CA 15-3 in persons with cancerous breast tumors however CA 15.3 test is not specific for breast cancer because levels are also increased in patients with gastric, colorectal, lung, pancreas, ovarian, uterine, and cervical cancers. CA 15.3 does not cause cancer.

Why the CA 15.3 is test done?
CA 15-3 concentrations tend to increase as the cancer grows. The highest levels of CA 15.3 are seen when the cancer has spread to the bones and/or the liver. CA- 15.3 test is done to help determine cancer characteristics to monitor the response to treatment of invasive breast cancer and to watch for the recurrence of the disease. Increasing concentrations of CA- 15.3 over time indicate that person is not responding to treatment or that the cancer is recurring.

What are the common signs/symptoms when the CA 15.3 test is done?

  • Paget's disease of the breast
  • Lump or mass in the breast
  • Lump that is painless, hard, and has uneven edges
  • Swelling of all or part of the breast
  • Skin irritation or dimpling
  • Breast pain
  • Nipple pain or the nipple turning inward
  • Redness, scaliness, or thickening of the nipple or breast skin
  • Nipple discharge other than breast milk

What should I do before the CA 15.3 test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)


Collection of blood from a vein, usually from the arm.

No Fasting Required.

No other special preparations required.

* Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my CA 15.3 test results?

Reference Range*


00 to 32.4 U/ml


‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the CA 15.3 test

  • Lung
  • Pancreatic
  • Ovarian
  • Liver
  • Colorectal cancers
  • Pancreatic cancer
  • Cirrhosis
  • Benign breast disorders

Other tests related to the CA 15.3 test

  • CA 27.29
  • Tumor markers
  • CEA
  • Her2/neu
  • Hormone Receptor Status
  • Gene Expression Tests for Breast Cancer