Definition

A CA 15-3 test is a blood test utilized to monitor specific types of cancer by measuring CA 15-3 levels in the blood. CA 15-3 is an antigen often present in breast tissue. Antigens are proteins that serve as distinctive markers for a cell that causes the body to make an immune response.

CA 15-3 are tumor markers that provide information about malignancy. This term encompasses any material present in cancer cells or other cells that are responding to cancer, either produced by these cells or found within them. Occasionally, specific non-malignant diseases may also produce tumor markers.

CA 15-3 is a substance that stimulates your immune system. Certain types of cancer cells secrete the CA 15-3 antigen into the bloodstream. Although the CA 15-3 antigen itself does not initiate cancer, its concentration can increase as cancer cells proliferate, in tandem with the growth of a tumor.

Recurrence of breast cancer predominantly releases CA 15-3, making it the most common cancer type associated with this antigen.  Breast cancers elevate CA 15-3 levels, releasing this substance into the bloodstream.

We also have an article on breast cancer which you can read here: Breast Carcinoma - Definition, Risk Factors and Management.

Indication

CA 15-3 serves as a tumor marker. These markers tend to rise as the cancer becomes more severe and drop as the tumor shrinks due to cancer treatment. It is one of a number of tumor markers used to monitor individuals with stage 4 (metastatic) breast cancer. However, it is not recommended to use the test to identify recurrences of breast cancer, even though certain oncologists (specialists in the treatment of cancer) may employ it.

The CA 15-3 test monitors breast cancer and its response to treatment. Physicians may recommend a CA 15-3 test for individuals diagnosed with advanced breast cancer.

Physicians do not use CA 15-3 as a screening or diagnostic tool for detecting breast cancer. Some individuals diagnosed with breast cancer may exhibit low levels of CA 15-3. The test is not as useful for individuals with early-stage breast cancer, as less than 50% of these instances will exhibit increased CA 15-3 levels.

Contraindication

There are no individuals for whom it is advised against to check their serum CA 15-3 level; everyone is eligible to undergo blood tests for monitoring the levels of CA 15-3 in their bodies.

Preparations Prior to Test

The test can be conducted at a hospital, clinic, or laboratory. There is no need to prepare for this test. Ensure that your healthcare provider is aware of all medications, vitamins, supplements or herbs you are currently taking. This encompasses over-the-counter medications and any illicit substances you may consume. 

Specific drugs and supplements have the potential to affect the accuracy of the CA 15-3 test. One of these compounds is biotin, which is sometimes referred to as vitamin B7, vitamin H, or coenzyme R. The CA 15-3 test depends on the interaction between biotin and the CA 15-3 antigen. However, excessive consumption of biotin can potentially interfere with the accuracy of the test.

Although the suggested daily intake of biotin is unlikely to have any detrimental effects, taking large doses of biotin supplements may result in inaccurate test results showing false negatives. Stop the consumption of any supplement that contains a biotin dosage over 0.03 milligrams, starting 72 hours before the test.

Test Procedures

A healthcare professional will extract a blood sample from a vein, usually in your arm, using a tiny needle. Once the needle is placed, a little sample of blood will be drawn into a test tube. You may experience a slight stinging sensation when the needle is inserted or removed.

Normal and Abnormal Values

The values of CA 15-3 could vary based on age, gender, and general health. There may also be slight variations in normal value ranges across various laboratories. The maximum acceptable value for the CA 15-3 test is 30 U/mL or below. Elevated levels of CA 15-3 may indicate the progression of tumors.

Results and Suggestions (Follow-Up Tests)

Physicians assess the outcomes of this test alongside the patient's other medical information. Typically, a higher CA 15-3 level indicates a more advanced stage of breast cancer and a larger volume of cancer cells in the body. CA 15-3 levels typically increase in correlation with cancer progression. The presence of elevated CA 15-3 levels is frequently observed in cases of metastatic breast cancer, particularly when the cancer has metastasized to the bones or liver. 

Increasing levels of CA 15-3 over a period of time may suggest that an individual is unresponsive to therapy or that the cancer has recurred. The efficacy of the treatment may be demonstrated by lowering or returning to normal levels of CA 15-3.

Occasionally, an individual with CA 15-3 levels within the normal range might still be afflicted with breast cancer, because normal levels does not guarantee the absence of breast cancer in an individual. The levels of CA 15-3 may not be high enough to be detected yet. Alternatively, around 20% to 25% of patients with advanced breast cancer have tumors that do not release CA 15-3.

It is crucial to understand that a positive CA 15-3 test result does not necessarily indicate breast cancer presence or recurrence. There are other factors that can cause CA 15-3 to be present in your bloodstream. Several illnesses, such as lung, pancreatic, ovarian, prostate, and colon cancer, as well as cirrhosis, hepatitis, and non-cancerous breast problems, slightly to moderately increase CA 15-3 levels. Additionally, a small percentage of seemingly healthy people may also have elevated CA 15-3 levels.

Consult to The Right Doctor

Test results can differ based on factors such as age, gender, medical history, or other factors such as the utilized laboratory. Healthcare professionals do not rely only on a CA 15-3 blood test to assess your response to cancer treatment, even though it can yield some helpful information.

Because antigen levels can fluctuate for a variety of reasons, it is important to confirm the results of this test with other diagnostic procedures. If you would like to discuss the meaning of the test results with your physician or oncologist, do so.

Want to know information about the results of laboratory, radiology and other examination results? Click here!