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Tumor markers, also known as tumor markers, are specific substances whose presence or elevated levels in the body suggests a disease. The detection of a tumor marker during screening tests often makes it possible to diagnose cancer at a very early stage. Check which markers are worth testing when suspecting specific diseases.
Tumor markers – what are they?
Cancer markers are substances that are released by or produced by the body in response to cancer. By measuring these markers in blood, urine, or other body fluids, they can be used to monitor cancer development, check for relapses, and sometimes to aid in screening and diagnosis.
Most tumor markers are proteins, but DNA changes such as mutations and other changes can also be used as biomarkers or tumor markers. The tumor marker can be taken from body fluids or from a sample of tumor tissue. Tumor marker results are usually not used for diagnosis alone, but may provide some clues when combined with clinical symptoms and imaging tests.
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Tumor markers – the aim of the study
There are a number of reasons why you may want to test for tumor markers. Among other things, in order to:
- monitor tumor development – The most common use of tumor markers is to track the development of a diagnosed tumor. In this situation, a decrease in the level of a tumor marker may mean that the tumor is shrinking (in other words, that the treatment is working), while an increase in the level may mean that the tumor is progressing.
- tumor recurrence monitoring – in some cancers, an increase in a specific tumor marker may indicate the tumor has come back,
- help diagnose cancer – Tumor markers are not used alone to diagnose cancer, but they can provide some supportive information.
- screen for cancer – An example of a tumor marker used for screening is the PSA prostate cancer test. PSA can be used both as a screening test and for tumor monitoring. In some cases, a tumor marker may be used to screen people who are at high risk of developing a particular tumor, but not in the general population.
- help determine the stage of the tumor – in some cases, tumor markers may be helpful in determining the stage of the tumor, which is important in selecting the best treatment options.
- help diagnose metastases – if the level of a specific tumor marker is very high, it may suggest that the tumor is not only growing but has spread (metastasized) to other areas of the body,
- estimate prognosis – in some cases, higher levels of a specific tumor marker may indicate a deterioration in the prognosis of cancer treatment.
- determine the choice of treatment – Gene mutations and other genomic changes can be used to determine whether targeted therapy is indicated, whether you have developed resistance to targeted therapy, and predict prognosis. When genetic biomarkers are used to define treatment, this is known as precision medicine.
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Tumor markers – the course of the study
Your doctor will take a sample of your body fluid or tumor tissue and send it to a laboratory to measure the tumor marker level. In the case of protein tumor markers, blood tests are most often performedbut can also be done from urine, stool, cerebrospinal fluid, peritoneal fluid (abdominal fluid), or pleural fluid.
Health cells in the body produce many markers, but these can be produced in much greater amounts by cancer cells (or in response to cancer cells). When tumor markers are present in greater amounts, healthcare professionals refer to the marker as “overexpression”.
Testing for tumor markers is very often most valuable when repeated to look at the progress of a tumor. If your laboratory test result is abnormal, your doctor will order additional tests. Tumor markers should always be used in conjunction with other tests, such as biopsies and imaging tests, to assess tumor progression.
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Tumor markers – restrictions in use
There are a number of limitations to the use of tumor marker testing to monitor tumor development. Some of them are:
- no tumor markers for some types of cancer – some types of tumors do not produce or cause the production of any tumor markers,
- false result – in some types of cancer, especially in the early stages, the tumor markers may not be elevated,
- false positive – for some tumor markers, there are a number of benign conditions that can also increase the markers. For example, CA-125 may be elevated in ovarian cancer, but also uterine fibroids, pregnancy and liver disease.
- Czas – the level of a tumor marker at some point may not necessarily reflect the development of a tumor. For example, if a tumor responds to treatment, it may take some time for a tumor marker to decrease, and if tumor cells are destroyed, the level of the markers may even rise for some time.
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Tumor markers – division of markers
The classification of tumor markers is as follows:
- characteristic antigens for cancer: these are elements that are not found in normal cells,
- fetal-embryonic antigens: they are found in the tissues and blood of the fetus and have the ability to disappear after a baby is born. Tumor markers: CEA, AFP.
- placental antigens: they most often occur in pregnant women and die after childbirth. Tumor markers: HCG, HPL.
- tumor antigens: they are characterized by the fact that they are produced by healthy as well as by cancer cells. Tumor markers: CA 19-9; CA 125; CA 15-3.
- enzymes: in a healthy person they occur under normal conditions, while in a sick person the amount of their production is completely disturbed. Tumor markers: PAP; PSA; NSE.
- ectopic hormones: this type of hormones occurs naturally in our body, but when we get cancer, their amount is produced in large amounts by cancer cells. Tumor markers: pituitary hormones: ACHT, ADH, TSH; thyroid and parathyroid hormones: PTH and calcitonin; adrenal medulla hormones: catecholamines.
- among other substances produced during cancer (by cells), we can mention: cytokines, acute phase proteins, inactive proteins.
Tumor markers – types
The list of confirmed tumor markers is very long, but several of them deserve special attention.
Tumor markers – CA 125
CA 125 is a marker used in the diagnosis of ovarian cancer. As much as 83 percent. women with this cancer have increased levels of this substance in the body. At the same time, among healthy people, only 1-2 percent. has an elevated level of CA 125, which makes this marker quite accurate. In addition to ovarian cancer, CA 125 may also indicate kidney or lung cancer; sometimes it also appears in endometriosis.
Tumor markers – PSA
PSA is a marker of prostate cancer. It is characteristic of this organ and sometimes it also appears in other diseases of the prostate gland, for example inflammation. The norm of PSA concentration varies depending on the age of the man. The first examination should be performed around the age of 40 and then systematically repeated.
Tumor markers – CA 72-4
It is also an important marker AC 72-4because this compound is not found in normal tissues at all. On the other hand, an increased level of this marker may indicate adenomas of various locations: cancer of the stomach, colon, esophagus or ovary, and therefore additional diagnostic tests are necessary if the level of this marker is elevated.
Tumor markers – AFP
AFP is most often performed when liver or testicular cancer (other than seminomas) is suspected. The amount of AFP in the body after birth slowly declines and is no longer produced. In patients who suffer from cirrhosis of the liver, this marker may be elevated, the same applies to: people with hepatitis caused by HBV.
Tumor markers – CEA
CEA is an antigen, high levels of which appear in the case of cancer: colon, pancreas, liver, breast, lung, bladder. In patients with colorectal cancer, the examination of the level of this marker is used by doctors to monitor the patients. In utero, we produce the CEA marker in large amounts, and then it is released by the pancreas and the cells of the gastrointestinal tract.
After childbirth, there are traces of this antigen in our body. Increased CEA levels, in addition to the above-mentioned cases, also appear in hepatitis; ulcerative enteritis or alcoholics suffering from cirrhosis of the liver.
Tumor markers – beta-HCG
Beta HCG it is a marker found in trophoblastic disease and acinar retinitis; in germ cell and testicular tumors. This antigen appears in the blood of pregnant women because it is produced by the cells in the placenta.
Tumor markers – CA 15-3
AC 15-3 is a neoplastic antigen, the elevated concentration of which is detected in breast cancer with accompanying metastases in various organs.
Tumor markers – calcitonin
And calcitonin is a marker that is characteristic of medullary carcinoma (thyroid cancer). It can be detected both during diagnosis, disease monitoring and after treatment.
Tumor markers – contraindications
The risks associated with testing tumor markers are primarily related to the procedure used to obtain fluid or tissue for testing – whether it is blood sampling, thoracocentesis to obtain pleural fluid, or a biopsy to obtain a tissue sample.
If only this test is used, tumor markers may provide inaccurate, false positive or false negative information, leading to suboptimal treatment.
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