The cancer antigen, 15.3, is a biological tumour marker that predicts the progression of breast cancer and response to treatment, and indicates the chances of recurrence. CA 15.3 is a biological molecule that is normally secreted by breast cells. However, in breast cancer patients, a higher amount is secreted by the malignant cells and this can enter the bloodstream. The molecule is secreted less in a localised breast tumour, but in the advanced stages of the disease, the test is highly useful for checking the prognosis.
How is the CA 15.3 test done?
A sample of blood is collected by your healthcare provider and it is analysed using various assay kits like enzyme-linked immunoassay, chemiluminescence, and radioimmunoassay in the laboratory for detecting the antigen. The fresh blood sample is used for treatment purposes and for biomedical research; frozen human blood samples are used.
How can we understand the test results of the CA 15.3 test?
The reference range of this antigen should be less than 25KU/l in 95% of normal individuals and 88% of benign cancer cases, but its upper limit will vary according to the amount shed by the malignant tumour cells.
Why do I need the CA 15.3 test?
The test is used to detect advanced breast cancer lesions with chances of metastasis and recurrence. It also helps to know how well the patient is responding to the treatmentÂ
What happens during the CA 15.3 test?
 A sample of blood will be drawn by your healthcare laboratory and will be analysed in a medical laboratory. It is advisable to do the test in the same laboratory every time during follow-up as different laboratories follow different techniques and standards.
What is the normal CA 15.3 level?
The CA 15.3 level in a normal individual should be below 25 KU/l.
Can we use CA 15.3 for screening of breast cancer?
No, this test cannot be used for screening breast cancer as it is also secreted by normal breast cells and lacks sensitivity and specificity for screening procedures.
What are the other conditions wherein there is an elevated CA 15.3 level?
CA 15.3 also seems to be elevated in conditions like liver, lung or ovarian diseases.Â
Are there any alternatives to the CA 15.3 test ?
Yes, CA 27-29 is a breast cancer tumour marker similar to CA 15.3.
Should I take any preparations before the test?
Follow the instructions given by your healthcare provider. Avoid drugs like biotin and afinitor as they can interfere with the test results.Â
How accurate is the CA 15.3 test?
The CA 15.3 test is highly specific in advanced stages of breast cancer. However, the upper reference range of the molecule varies based on the tumour.Â
Does the test pose any significant risk?
No, the test does not pose any significant risk as such, other than the rare chances of infection and bleeding from the site of blood collection.
What are the other tests suggested along with the CA 15.3 test for breast cancer?
Doctors suggest evaluation of oestrogen and progesterone receptors and HER2 and gene expression to analyse the patient’s breast cancer.
For further information, book an appointment and get a free second opinion at Yashoda hospitals
1) Coppola, L., Cianflone, A., Pane, K. et al. The impact of different preanalytical methods related to CA 15.3 determination in frozen human blood samples: a systematic review. Syst Rev 10, 102 (2021).
2)Al-azawi, D., Kelly, G., Myers, E. et al. CA 15.3 is predictive of response and disease recurrence following treatment in locally advanced breast cancer. BMC Cancer 6, 220 (2006).
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