Generality
CA 15-3 (acronym for Cancer Antigen 15-3 ) is a protein, used as a tumor marker for breast cancer .
CA 15-3 is normally produced by breast cells; this protein, therefore, does NOT cause malignancy, but increases following its development.
What's this
Tumor Antigen 15-3 (CA 15-3) is a protein produced by breast cells.
In many of the people suffering from malignant breast cancer, an increase in the production of CA 15-3 and of the related tumor antigen 27.29 is observed (frequently but not always).
This marker is especially useful for monitoring the progression of advanced disease and verifying the effectiveness of the treatments undertaken. Furthermore, the relief of the tumor Antigen 15-3 over time keeps the possible resumption of the neoplastic process under control.
Why do you measure
Tumor antigen 15-3 belongs to the category of so-called tumor "markers", ie those substances that can be found in increased amounts in the blood, urine or other body fluids in the presence of certain neoplasms.
In many cases, this marker is produced in excess by breast cancer cells and enters the bloodstream.
The 15-3 tumor antigen test can be requested as a support in the determination of tumor characteristics and in the evaluation of therapeutic options, following the diagnosis of advanced breast cancer .
It should be noted that the performance of this test is not indicated in all situations, since the CA 15-3 is not elevated in all women with breast cancer .
Diagnostic utility
The CA 15-3 dosage is not used neither for diagnosis nor for breast cancer screening; it is used instead to follow its evolution over time and monitor the effectiveness of the treatments undertaken.
The examination, in fact, tends to be positive only in the advanced stages, while in women with a disease still in its initial phase it rarely shows high values (10-20% of the subjects, against a 70-95% in the presence of metastases).
As mentioned, low concentrations of CA 15-3 do not exclude the presence of breast cancer.
Also the specificity of the test is not optimal, given that the levels of CA 15-3 may increase in the presence of ovarian, colon-rectal, lung and prostate cancer, benign breast cancers, ovarian diseases, endometriosis, rheumatic diseases, pelvic inflammation, cirrhosis and hepatitis.
When is the exam prescribed?
CA 15-3 is a tumor marker useful for monitoring invasive forms of breast cancer. The examination can be requested periodically to monitor the effectiveness of the treatment and as a support in detecting the eventual recurrence of the disease (recurrence). Therefore, your doctor may prescribe this examination after or during treatment of invasive breast cancer.
The CA 15-3 is not prescribed, however, when the diagnosed breast cancer is still at the initial stage (ie before it metastasizes), since at this stage the concentrations of the marker are often not high.
In any case, the outcome of this examination is considered together with other clinical evaluations and the result of other tests (eg gene expression profile in breast cancer, Her-2 / neu and estrogen / progesterone receptor).
Normal values
CA 15-3 levels are measured in a blood sample taken from a vein in the forearm, just like any other traditional blood test.
The normal values of CA 15-3 are between 0 and 32.4 U / ml (units per milliliter of blood).
Note: the reference interval may change according to age, sex and instrumentation used in the analysis laboratory. For this reason, it is preferable to consult the ranges listed directly on the report.
CA 15-3 High - Causes
The value of CA 15-3 is increased compared to the norm in less than 50% of women with localized tumor at the early stage or with a small neoplastic mass.
On the other hand, tumor antigen increases considerably in about 80% of women with advanced or metastatic breast cancer .
In breast cancer already undergoing metastasis, the highest concentrations of CA 15-3 are observed when the tumor has spread to the bones and / or liver.
Warning! Normal CA 15-3 concentrations do not ensure that the person does not have a localized or metastatic breast tumor:
- In some cases, the tumor may still be at an early stage, such as not to have sufficiently high tumor antigen concentrations 15-3.
- At other times, a type of breast cancer may be present (20-25% of the cases) characterized by low tumor antigen levels, despite the advanced stage.
CA 15-3 can also be moderately elevated in healthy people or those with other types of cancer (for example: malignant tumors of the colon, lung, pancreas, ovary or prostate).
An increase in tumor antigen 15-3 can also be found in various other types of disease / clinical conditions, such as:
- Cirrhosis;
- Hepatitis
- Some benign diseases of the breast.
High levels of this marker may also be present in rheumatic diseases.
The increase in CA 15-3 in non-tumor pathologies tends to remain stable over time.
How to measure it
The CA 15-3 exam is a laboratory analysis that is performed on a blood sample taken from the patient's arm.
Preparation
For the analysis of the CA 15-3, no special preparation is required.
In some cases, a fast of at least 8 hours may be recommended, to prevent the food from interfering with the result. During this period, a small amount of water can be taken.
Interpretation of Results
High CA 15-3 values are indicative of the presence of a breast tumor. In general, the greater the concentration of the antigen in the bloodstream and the more advanced the stage of breast cancer and the large neoplastic mass.
However, it should be remembered that a moderate increase in the concentration of this marker can also be observed during rheumatic diseases or other types of pathologies / clinical conditions, such as cirrhosis, hepatitis and certain benign diseases of the breast. For this reason, if the result of the exam is higher than the norm, the doctor will recommend the appropriate investigations to assess whether or not it is a tumor.
If the CA 15-3 dosage was performed as part of the monitoring of a therapeutic protocol to counteract a neoplastic process, the increase in the marker concentration over time may indicate the lack of response to the treatments (which must therefore be modified ) or the presence of a repeat offender.
Usefulness in monitoring breast cancer
As anticipated, the 15-3 tumor antigen is mainly used to monitor the treatment of women with breast cancer, especially in the advanced and disseminated phase. Its concentration, in fact, tends to increase with the growth of cancer and with its propagation to other tissues, in particular to the bones and the liver.
The dosage of CA 15-3 is often carried out in periodic checks after removal of the tumor, so as to detect any recurrences or metastases. Depending on the case, an increase in its values indicates a lack of response to treatment, a progression of carcinoma or a relapse.
- A 25% increase in serum CA 15-3 is associated with progression of carcinoma.
- A decrease of more than 25% is associated with a positive response to treatment.
- A 50% decrease is associated with a positive response to treatment and a regression of the disease.
- An increase or decrease of less than 25% is associated with a stabilization of the disease.
The CA 15-3 dosage can be performed together or as an alternative to the tumor antigen 27-29.
As for the ability to detect recurrences in early stages, CA 15-3 is a more sensitive tumor marker than CEA (carcino-embryonic antigen); the two tests can still be used together to monitor the evolution of the therapy and the effectiveness of the treatment.
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