Cancer markers

How cancer is diagnosed

European Clinic, Naked Science

Many people have heard about cancer markers, but not everyone knows what they are, how they work, what cancer is in general and why the analysis for oncopathology is not always accurate. This is told by the chief physician of the European Clinic specializing in the treatment of malignant tumors, Andrey Pylev.

Cancer markers are antigens associated with various tumors, containing mainly special proteins or carbohydrate components that appear in human blood when malignant or benign formations occur.

In total, today scientists have identified about 200 different cancer markers, but in laboratory studies they use no more than 20-30 of the most informative types for diagnosis.

Specialists divide cancer markers into two groups. The first is qualitatively different, tumor–specific markers. They are compounds that are produced by a tumor, and are normally absent in the body of a healthy person.

Therefore, even a slight increase in them indicates some kind of violation and serves as a cause for alarm.

The second group is quantitatively different cancer markers. These substances are normally always present in human blood, but in a very small volume. Their growth almost always indicates a neoplasm developing in the body, but not always malignant.

At the moment , the following are most often used in medical practice:

• AFP (alpha-fetoprotein) is associated with liver cancer in 90% of cases;
• PSA (Prostate specific antigen) correlates with prostate cancer;
• CA 125 is a protein associated with tumors of the female reproductive system;
• CA 15-3 is a specific protein for breast cancer;
• CA 72-4 is specific for various carcinomas localized in the gastrointestinal tract, as well as the mammary and pancreas;
• REA (cancer-embryonic antigen) it may indicate gastrointestinal tumors, primarily colorectal malignancies, as well as cancer of the female reproductive system and mammary glands;
• Beta-2-microglobulin increases in response to multiple myeloma and lymphoma.

History of discovery

The date of the first mention of cancer markers in the world is considered to be 1845. A young doctor, Ben Jones, worked at St. George's Hospital in London. It was he who discovered a specific protein in the urine analysis, which later became known as Ben-Jones.

This discovery gave impetus to the development of biochemistry and with it immunology, which allowed scientists to identify even more proteins, which we now call cancer markers.

In Russia, one of the most significant works in the world of cancer diagnostics was the study of academician Harry Abelev and Lev Zilber. In the mid-1950s, Abelev and his colleagues were extremely enthusiastic about the then–new immunodiffusion analysis - a powerful tool in the study and comparison of complex protein mixtures.

Scientists have developed a methodological approach for comparing normal and tumor tissues and isolating tumor-specific antigens.

They were used to study liver cancer in mice. The results were inspiring.

Quite unexpectedly, another study found the same antigen in a mouse embryo, where it was present in huge quantities – and not only in the liver, but also in all organs of the fetus.

It soon became clear that this antigen is the main component of embryonic serum – embryonic serum α-globulin, later called alpha-fetoprotein (AFP).

The AFP produced by the fetus and mouse hepatomas in tissue culture was identical. These data were reported at the VIII Anti-Cancer Congress, which was held in Moscow in July 1962.

AFP is widely used in cancer clinics and obstetrics. It is the best marker for studying the regulation of tissue-specific and embryo-specific proteins in normal development. Now it is actively used in the diagnosis of liver cancer, ovarian cancer in women and testicular cancer in men.

Dynamic control

How are cancer markers used in modern medicine? The titer (concentration expressed by the amount) of a specific protein is directly dependent on the size of the tumor, so it is convenient to use an analysis for cancer markers to assess the effectiveness of the treatment.

This is its main purpose. The patient receives various types of therapy, such as chemo or radiation, and by periodically repeating the analysis, it is possible to judge how the body responds to it.

An increase in the titer indicates that the tumor is growing, which means that therapy is not suitable and you need to change the strategy. The decrease indicates that the tumor is decreasing and the prescribed treatment should be continued.

In addition, patients who have received radical treatment (surgical removal of the tumor) and have been living for a long time without signs of the disease should also periodically take specific cancer markers.

In some cases, they can observe the so-called marker progression: when there are no signs of the disease yet and an instrumental examination shows nothing, but the markers are growing.

Such a picture indicates a relapse of the disease. Most often this can be observed in women who have had cancer of the reproductive system.

Clarification of the diagnosis

In some cases, cancer markers are used for clarifying diagnostics, against the background of already identified oncopathology.

For example, if a patient has pancreatic cancer, but there are difficulties in carrying out a morphological study to make a diagnosis, an analysis is prescribed for the cancer marker CA 19.9, its increase indicates ductal pancreatic cancer.

The norm of the tumor marker is up to 10 units / ml, an increase in the level to 1000 units / ml or more indicates that the malignant process has reached the lymphatic system. If a patient with viral hepatitis B or C with cirrhosis and a large tumor node in the liver has a level of AFP that exceeds the norm by 1000 times, there is no doubt about the diagnosis: it's cancer.

And according to all international standards, in this case, it is possible not to do a biopsy, but to establish a diagnosis based on the clinical picture and an analysis for a cancer marker.

Here I want to make a small digression and tell you what cancer is in general. The fact is that cancer as a single disease does not exist. This is a set of diseases that have different causes and affect different tissues and organs.

What can be seen even from the names of tumors. Thus, tumors from cells of epidermal origin are called carcinomas, and from connective and muscle tissue – sarcomas.

In addition, there are a number of tumors that are not included in these groups and have their own names (for example, leukemia, glioma, retinoblastoma, and so on).

Cancer is the result of a malfunction in two systems. One cellular system is transformed, and its cells begin to actively divide, and the other – the immune system – recognizes these cells alien to the body as its own and does not destroy them, but begins to protect them.

All these diseases require a comprehensive diagnostic approach, cancer markers alone are not enough.

Medical centers and laboratories offer to take tests for certain cancer markers not only if a malignant process is suspected, but also for preventive purposes, as part of onco-check-up programs.

The problem is that with the exception of PSA, which shows the presence of prostate cancer, the other markers are not very specific: even the most accurate of them have a sensitivity of no more than 70%.

This means, firstly, that they can grow not only with the development of a cancerous tumor of an organ, but also with its inflammation or the formation of any other benign process.

Moreover, if any person passes an analysis for 20-30 of the most common markers, it is quite likely that one or even several of them go beyond the norm.

This is due to the fact that there are no completely healthy people. Someone suffers from chronic diseases or does not notice sluggish inflammation and lives quietly with it.

Someone often has benign neoplasms. All this can blur the picture and cause a false positive result.

Secondly, there is always a group of patients for whom such a diagnosis is ineffective: in the presence of a tumor and proper laboratory testing, the result of the analysis turns out to be negative.

Thus, using cancer markers for primary diagnosis is unprofessional, and sometimes even dangerous, because a person with a false negative result will be sure that everything is fine with him and will lose precious time.

The role of cancer markers in the monitoring and treatment of cancer is very high, the main thing is to use them on time and for the right purposes.

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