Oncomarkers, or tumor markers, are specific molecules that are produced by tumor cells or healthy cells in response to tumorigenesis. Usually, oncomarkers are proteins, but they can also be represented by enzymes or hormones.
Tumor marker tests can help your doctor learn more about the tumor and decide on treatment tactics. The results of the tests are only used in a comprehensive diagnosis in combination with the data of the examination and imaging studies, not separately. This is due to the fact that oncomarkers do not have high specificity and sensitivity, that is, their level in the blood can increase for many other reasons not related to cancer.
Usually, doctors use oncomarker tests to confirm an already established diagnosis, track the course of the disease, and adjust medications or other therapeutic prescriptions.
Main types of oncomarkers
There are several principles for classifying oncomarkers. They are usually grouped by chemical structure or by the function they perform in the body.
Types of oncomarkers by chemical structure:
- glycoproteins – complexes of proteins with carbohydrates;
- polypeptides – long chains of amino acids;
- carbohydrate determinants of glycoproteins are small chains of carbohydrates that are attached to the protein part of the protein-carbohydrate complex;
- glycolipids are molecules composed of fats and carbohydrates;
- proteins;
- polyamines – molecules that are made up of chains of elements containing nitrogen;
- immunoglobulins – protein molecules, also known as antibodies, that are produced by cells of the immune system.
Types of oncomarkers by biological function:
- oncofetal antigens;
- enzymes (enzymes);
- hormones – adrenocorticotropic hormone, antidiuretic hormone, calcitonin, paratgormone, prolactin;
- receptors – progesterone receptors, estrogen receptors.
In addition, there are compounds whose role is not fully elucidated, but they are also used as cancer markers. Such compounds include ferritin, beta-2-microglobulin, and some other immunoglobulins.
Why do blood tests for oncomarkers?
Oncomarker tests are performed to confirm the diagnosis, assess the effectiveness of treatment, predict the disease and detect recurrence.
The main indications for the analysis:
- Monitoring the course of the disease: a decrease in marker levels may indicate the effect of treatment, while an increase may indicate tumor progression.
- Diagnosis of cancer recurrence: an increase in the marker may indicate that tumor cells have become active.
- Cancer screening: for example, a test to detect prostate cancer at an asymptomatic stage.
- Metastasis diagnosis: high levels of a marker may indicate tumor spread.
- Prognosis assessment: high levels of some markers may indicate a poorer prognosis.
In rare cases, the tests are prescribed in suspicion of cancer, but the results are evaluated in conjunction with other studies.
What the deviation of oncomarker values from the norm indicates
Changes in the level of oncomarkers in biological fluids and tissues can indicate various conditions, including malignant neoplasms, inflammatory processes, benign tumors or other diseases.
Possible causes of abnormalities in oncomarkers:
- malignant tumors – the most significant cause of markedly elevated oncomarker levels;
- benign tumors – some benign tumors can also lead to elevated levels of oncomarkers, although usually to a lesser extent than malignant tumors;
- inflammatory processes in the body, such as hepatitis, pancreatitis or gastritis, can lead to elevated levels of certain cancer markers;
- infectious diseases – viral hepatitis, genitourinary and some other infections can also lead to a temporary increase in cancer markers;
- physiologic conditions – pregnancy, severe stress, exhausting physical activity, and dietary habits may affect the content of oncomarkers.
Limitations of the use of oncomarkers
Oncomarkers are controversial indicators of tumorigenesis, as their levels can be elevated in many other conditions. Because of this, oncologic laboratory screening is usually performed only in conjunction with other diagnostic methods and when indicated.
The main limitations to the use of oncomarkers in cancer diagnosis are:
- Low specificity. Oncomarkers may be elevated in various benign tumors and inflammatory diseases, which can lead to false positive results. In addition, tumors are of different types, and some of the oncomarkers may indicate one type while others may indicate several, so it is not possible to make an accurate diagnosis based on them;
- Limited sensitivity for some tumors. Not all cancers are accompanied by elevated levels of oncomarkers, especially in the early stages of the disease, and some oncomarkers may remain within normal limits even in the fourth stage of cancer;
- The influence of external factors. Medical procedures and medications used to treat cancer can themselves cause cancer marker levels to deviate from normal, making it difficult to interpret the results.
Although cancer markers help us understand how some tumors develop and how they respond to treatment, their sensitivity and specificity are not sufficient for diagnosis. To make an accurate diagnosis, results of other tests are required, such as biopsy followed by histology – a detailed examination of cells under a microscope.
How to give blood for oncomarkers correctly
To make the results of the oncomarker test more reliable, doctors recommend following certain rules of preparation.
The main recommendations for preparing for the oncomarker test:
- It is forbidden to drink alcohol 48 hours before the test.
- 24 hours before the analysis you should refuse fatty, fried and spicy food, avoid intense physical activity and stress.
- Blood for analysis is recommended to take in the morning on an empty stomach after at least 8-10 hours of hunger. If dynamic monitoring is required, blood for repeated tests should be taken at the same time as for an earlier study.
- In the morning before the analysis you can drink only water. Tea, coffee and other drinks can be drunk after the study.
- 2-3 hours before the analysis (it is better as early as possible) you should not smoke.
- It is desirable to arrive a little early for the analysis and spend 10-15 minutes at rest in the laboratory department.
Conclusion
Oncomarker tests are a valuable tool for monitoring cancer, assessing treatment effectiveness, detecting recurrences, and evaluating prognosis. However, due to their limited specificity and sensitivity, these tests should not be used in isolation for cancer diagnosis. Abnormal levels of oncomarkers can indicate a range of conditions, including both malignant and benign tumors, as well as non-cancerous diseases. To ensure accurate results, oncomarker tests should be used alongside other diagnostic methods, such as imaging, biopsy, and histology. Proper preparation before the test is crucial for obtaining reliable results, and the interpretation of the findings must be done in a comprehensive clinical context.
