CA 15-3 Test


Last Updated December 20th, 2021

What is a CA 15-3 test?

Cancer antigen 15-3 (CA15-3) test is a blood test that is performed in order to monitor the response to therapy for breast cancer and to assess disease recurrence.

What is CA 15-3?

Cancer antigen 15-3 is a protein formed by many cells in the body, particularly the breast cells. It is found in the blood and is used as a tumor marker (also called serum marker or biomarker) in monitoring therapy for breast cancer.
However, breast cancer cells are not the only ones secreting this antigen. A plethora of malignancies produce this protein, namely

– Lung cancer (both small cell and non-small cell)
– Pancreatic cancer
-Endometrial cancer
-Ovarian cancer
-Hepatic cancer
– Colon cancer
-Prostate cancer

Why has my physician asked me to undergo a CA 15-3 test?

A CA 15-3 test is performed in order to assess the response of your breast cancer to therapy. It can also be used to detect any recurrence of this disease. Elevated levels of cancer antigen 15-3 are seen in approximately 60% of preoperative breast cancer cases and 80% of widespread metastatic breast cancer cases.

You will be asked by your physician to go for this test if you have already been diagnosed with invasive breast cancer and are undergoing therapy for the same.

CA 15-3 test is not endorsed as a screening tool to detect breast cancer in women because it is non-specific. Several other malignancies can lead to elevated CA 15-3 levels in the blood. Moreover, levels of CA 15-3 may be elevated in many benign diseases (including benign breast disorders) and even in healthy individuals.

I have a family history of breast cancer. Should I undergo CA 15-3 test?

No. The CA 15-3 test is not a screening tool for detecting breast cancer. Its levels are not elevated in early stages of breast cancer. Moreover, there are many other conditions (both benign and malignant) which can lead to elevated levels of CA 15-3 in your blood.

What are the non-cancerous conditions that can cause elevated levels of CA 15-3?

Elevated levels of CA 15-3 can be seen in many benign conditions. A few of them are listed below-

– Liver disorders (including chronic hepatitis and cirrhosis)
– Sarcoidosis
– PID (Pelvic inflammatory disease)
– SLE (Systemic lupus erythematosus)
Vitamin B12 deficiency
Levels of CA 15-3 are also found to be elevated during pregnancy and lactation.

Do I need to fast before a CA 15-3 test?

There is no need to fast before you undergo a CA 15-3 test. The presence or absence of food in your stomach does not alter the levels of this antigen in your blood and thus does not hamper with the test results.

Can I undergo a CA 15-3 test if I am pregnant?

Yes, you can safely undergo a CA 15-3 test if you are pregnant or breastfeeding your child. However, you need to inform your physician if you fit into the above-mentioned categories as the blood levels of CA 15-3 tend to be elevated during pregnancy and lactation.

What are the risks involved?

A cancer antigen 15-3 test is a blood test. It is easy to perform, safe and quick test. Complications are rarely seen. However, as this test involves the puncture of a vein to collect a blood sample, the following complications may arise-

– You may feel a stinging sensation when the needle pricks your skin.

– The act of puncturing a vein and drawing blood may be unnerving to some. You may feel dizziness at the sight of blood. It is advisable to distract yourself during this step if you are faint-hearted.

– A bruise at the sight of the prick may appear.

– In some cases, bleeding may be encountered at the site of venous invasion.

– A hematoma may form at the site of puncture.

There are chances of infection at the site of venesection at a later stage. If you encounter the presence of pus or signs of inflammation at the site, consult your physician.

What are the contraindications of a CA 15-3 test?

There are no absolute contra-indications to a CA 15-3 test. However, as it is a blood test including venesection, your physician may defer performing this test if you suffer from a bleeding tendency.

How should I prepare for a CA 15-3 test?

No specific preparations are to be done by you before embarking on a CA 15-3 test. However, you need to inform your physician about your medical history, and any medicines or supplements that you might be consuming at the time of the test. Inform him if you suffer from any coagulopathy or are on blood thinners. You also need to intimate your physician if you are pregnant or breastfeeding your child. The levels of CA 15-3 tend to get elevated in women who are pregnant or lactating.

How is a CA 15-3 test performed?

It is a blood test carried out on an outpatient basis unless you are already admitted in a hospital. A laboratory technician will escort you to the assigned place to collect blood sample for the test. The laboratories usually have designated collection points for retrieving samples for a test. The CA 15-3 test is easy to perform and consists of the following standard steps

– The technician will apply a tourniquet proximally to the site chosen for venipuncture. This makes the veins more prominent, allowing easier access. The median cubital vein (a superficial vein on the inside of your elbow) is commonly chosen.

– The area is cleaned with a disinfectant.

– A sterile, single use needle is used to puncture the vein and draw about 5 ml of blood.

– Pressure is applied to the vein with a sterile gauze after the needle is withdrawn. It stops bleeding at the site of puncture.

-Tourniquet is released.

– The blood sample is collected in a vial.

How long does the CA 15-3 test take?

The entire procedure is over in 5-10 minutes. In obese patients, and patients belonging to geriatric age group, venous access is sometimes difficult, leading to more than one prick. The time taken to collect a blood sample may get prolonged in such cases.

When can I get the results of a CA 15-3 test?

You can get the results of a CA 15-3 test on the same day (within 24 hours in some cases).

What do the results convey?

The reference range of serum CA 15-3 is less than 30 U/mL. Different laboratories use different methods to test for this antigen. So, if you are going for serial testing, it is advisable to stick to a single laboratory.

– A declining level of CA 15-3 indicates that the malignancy is responding to treatment.

– The higher the CA 15-3 levels, the more widespread is the breast cancer.

– As the tumor burden grows, so does the concentration of CA 15-3 in the blood.

– An increasing level of CA 15-3 antigen may also indicate that the anti-cancer therapy is not working. A stable value indicates that the tumor is not growing.

– A false high reading may be obtained if the test is performed too early during treatment.

What is the cost of undergoing a Cancer antigen 15-3 test in India?

The cost of a CA 15-3 test in India ranges from Rs 1000-1500. The actual cost may vary depending on the city you reside in and the diagnostic center that you choose for this test.

What are the advantages and limitations of a CA 15-3 test?

Advantages Limitations
It is a safe, easy to perform and quick test. It can be safely performed in pregnant and lactating women.It has low sensitivity in early-stage breast cancer.
The sensitivity and specificity are high for metastatic breast cancer.It has no clinical significance in breast cancers that do not secrete CA 15-3 tumor marker.
It can be used as an independent prognostic factor for patients of breast cancer.A falsely elevated result may be obtained in the first 4-6 weeks of therapy.
Any recurrence of breast malignancy can be detected well in advance (5-6 months) of any other sign/symptom or other tests.The overall sensitivity and specificity of CA 15-3 for all breast cancers are low. It needs to be supplemented by other tests in order to reach a conclusion.

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