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The term tumor markers is well known to those suffering from cancer. But what is it, what are markers for and how are they used in clinical practice?
They are sometimes referred to as tumor markers or indicators, but the most common term is tumor markers.
Cancer markers were discovered over 40 years ago. The first scientific works on their structure suggested that they may be specific to a specific tumor location. However, further research has shown that this is not always the case – the same marker is sometimes secreted by different cancer cells. Moreover – one type of cancer can give off different tumor markers. For example, elevated CA 19.9 levels may be associated with both pancreatic cancer and gastric cancer, while elevated CA 125 levels are characteristic of ovarian cancer. The same marker may also be found in other advanced malignant neoplasms, e.g. in adenocarcinoma of the cervix. However, there is overwhelming evidence that some of the markers almost 100 percent indicate a specific type of cancer.
Perfect marker
Cancer markers are multi-molecular substances that perform various biological functions. They are produced in the human body. Elevated serum levels of these markers are usually associated with neoplastic disease, but this is not always the case.
The diagnostic value of any neoplastic marker is determined by four features. So, an ideal marker should:
1. Have XNUMX% sensitivity, that is, its increased values should occur only in people suffering from malignant tumors.
2. Have XNUMX% specificity, which means that the level of a given marker remains within the normal range in healthy people or patients with non-neoplastic diseases.
3. Confirm the presence of a malignant tumor depending on the concentration of the marker (positive predictive value).
4. Exclude the presence of a malignant tumor depending on the concentration of the marker (negative predictive value).
Unfortunately, these conditions are met by only some markers, e.g. hCG (chorionic gonadotropin) in gestational trophoblastic disease, hCG and AFP (alpha-fetoprotein) in embryonic testicular tumors, PSA (prostate specific antigen) in prostate cancer, and calcitonin and thyroglobulin in thyroid cancer. Therefore, only some tumor markers in combination with other diagnostic methods have been used in screening. And so the PSA marker supports the diagnosis of prostate cancer, at a very early stage of development. In turn, AFP is characteristic of primary liver cancer and makes it possible to recognize it without a shadow of a doubt. But the diagnosis doesn’t stop there. It is also necessary to perform other specialized tests, such as ultrasound, mammography, cytology or x-rays or biopsy.
Not only cancer
When determining tumor markers, it must not be forgotten that some of them may have a slightly higher concentration than the standard provides. A slight increase in the concentration of standard tumor markers such as CEA (carcinoembryonic antigen), CA 125 (ovarian cancer antigen), CA 19.9 (an antigen associated with gastrointestinal cancer) also occurs in non-neoplastic diseases, especially those accompanied by inflammation. But it is not everything. The concentration of some markers may also change physiologically, e.g. with age the level of PSA (prostate antigen) will increase, which is related to the growth of the gland. In women whose ovarian hormonal function has terminated, a decrease in the concentration of the CA 125 marker may be observed. However, it should not be concluded that tumor markers are useless. On the contrary. Significantly elevated levels of tumor markers are likely to indicate not only the presence of a tumor, but also a very advanced disease development.
In clinical practice
Tumor markers are primarily used to monitor the effectiveness of treatment, most often when the cancer is located in the ovary, cervix, prostate, testicle, large intestine, pancreas, stomach, liver, lung, breast and thyroid gland.
When assessing the progress of treatment, doctors take into account the specific behavior of the levels of some markers. It is known that neoplastic cells, although they produce markers, do not always release them into the blood. Therefore, in a certain percentage of patients with malignant neoplasms, the concentration of markers may remain within the normal range, even when the disease is advanced.
In addition, in disseminated neoplastic disease, many markers may circulate in the blood that are not typical of the location of the neoplasm.
During chemotherapy or radiation therapy, you may develop very high levels of markers specific to your cancer, but this is usually due to the breakdown of the tumor and the release of more antigens into the blood, rather than a deterioration of the patient’s health.
After treatment, while continuing to monitor patients’ health, the determination of tumor markers together with other tests helps doctors assess the clinical condition of patients. The increasing concentration of the marker may precede the appearance of clinical symptoms of the disease for several weeks or even several months. However, it should be remembered that if the marker concentration remains normal, it does not exclude a neoplastic disease.
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Fashion for research
Most of us are afraid of cancer. This is normal even if there is no family history of cancer. But, according to oncologists, there is no need for each of us, as if in advance, to demand the determination of tumor markers. Such research makes sense if we belong to the high-risk group, i.e. when the same cancer has occurred in subsequent generations of our family, or at least in one case it developed before the age of 50.
Tumor markers are determined from a blood sample. This is a fairly simple test that can be performed in almost any laboratory. In order to make a correct diagnosis, it is important not only the presence of the marker in the blood, but above all its amount above the acceptable norm. If the norm is even significantly exceeded, it does not always mean cancer. Elevated levels of some markers may be associated with inflammation of the liver, pancreas or kidneys. Therefore, after conducting the test, a specialist interpretation of the obtained results is necessary. Without it, we will worry unnecessarily or we will downplay the existing threat.
Under the care of genetic clinics
If your family history indicates that you are at a higher risk, because breast or ovarian cancer has occurred in several generations – go to a genetic clinic. You cannot count on this way to protect yourself from the disease, but thanks to systematic check-ups, it will be detected early enough to be completely cured. Genetic clinics are located at all oncology centers in the country. You do not need a referral from a primary care physician to see an oncologist.