The nature of cancer
Repair the body
Cancer is not as terrible as a sweet cigarette. Deep inside, many people think so. Where does oncopathology come from, is it possible to "fix" humanity, how is cancer inherited and what is targeted therapy? This was told by the medical director of the pharmaceutical company Pfizer Oncology Maria Mukhina.
– Where do oncological diseases come from?
– Cancer is a disease of the genome. This means that it is caused by certain changes in the genes that control the work of our cells, especially how they grow and divide. Certain gene changes lead to the fact that cells escape from the control of growth and division, begin to divide intensively and abnormally, grow and become cancerous.
Cancer cells have more genetic changes than normal ones. At the same time, the oncopathology of each person has a unique combination of genetic changes.
As the tumor grows, additional secondary changes occur. Even within the same tumor, cancer cells can have different genetic changes. This phenomenon is called tumor heterogeneity.
– How do gene breakdowns occur in general and is it possible to fix them on a human scale?
– A gene is a piece of DNA. Accordingly, the breakdown of a gene is a breakdown of the DNA structure. There are many different kinds of DNA changes: some of them affect only one unit of DNA, called a nucleotide. One nucleotide can be replaced by another or completely absent.
Other changes include large stretches of DNA and may involve rearrangements, losses, or doubling of long sections of the molecule.
Sometimes the changes do not affect the sequence of the DNA itself, but the addition or removal of chemical labels called epigenetic modifications.
Repairing gene breakdowns on a human scale is an attractive task, but extremely difficult and, unfortunately, currently practically unrealizable. The development of tools for correcting mutations in a gene lags far behind diagnostic methods.
A person has an average of 30 thousand genes and four trillion cells, which, among other things, are regularly updated. For complete "healing", it is necessary to correct the mutation in each cell and at the same time not "spoil" other genes.
And taking into account the fact that each oncological patient has his own individual set of genetic changes in the tumor, the task becomes even more difficult. Various studies and developments are being carried out, but none of the studied methods has yet found practical application.
– What are the mechanisms of inheritance of oncological diseases?
– Genetic changes that contribute to the development of cancer can be inherited from our parents if these changes are present in the germ cells (eggs and sperm).
Such changes, called germline changes (germinogenic), are found in every cell of the offspring.
Inherited mutations play a major role in about 5-10% of all cancer cases. Researchers have linked mutations in genes with more than 50 hereditary syndromes that can predispose to the development of certain types of cancer.
At the same time, even if there is a mutation in the family that predisposes to cancer, not all offspring necessarily develop it.
Here are some examples of genes that may play a role in hereditary cancer syndromes – hereditary mutations in the BRCA1 and BRCA2 genes lead to breast and ovarian, pancreatic and prostate cancer syndrome; TP53 produces a protein that suppresses tumor growth, which leads to a higher risk of developing certain cancers; mutations in the PTEN gene are associated with Cowden's syndrome, a hereditary disease that increases the risk of breast and thyroid cancer, endometrial and other types of cancer.
Genetic tests can determine whether a person with signs of cancer syndrome has a hereditary mutation. These tests can also show whether family members have inherited the same mutation.
Sometimes it seems that cancer that is not associated with hereditary mutations also occurs in families. Indeed, the general environment or lifestyle (e.g. alcohol consumption, smoking) they can cause the development of similar types of cancer among members of the same family.
– Is prevention possible? What are its prospects: is it possible to prevent the development of cancer?
– It is usually impossible to know exactly why one person develops cancer and another does not. Studies have shown that certain risk factors, such as exposure to chemicals or other substances, as well as certain behaviors can increase the chances of developing cancer. They also include uncontrollable factors such as age and family history.
Prevention is a set of measures aimed at minimizing risk factors and strengthening protection factors. Let's analyze the main factors and possible preventive measures.
It has been proven, for example, that alcohol consumption can increase the risk of developing cancer of the mouth, throat, esophagus, larynx, liver and breast. The risk of getting sick is much higher among those who drink alcohol and smoke.
Smoking, by the way, is the main cause of death from cancer, causing many of its types, including cancer of the pancreas, colon and rectum, and others. There is no safe way to use tobacco.
But people who quit smoking, regardless of their age, have a significant increase in life expectancy. In addition, quitting smoking at the time of cancer diagnosis also reduces the risk of death.
Everyone also knows that ultraviolet radiation and radiation have a serious negative impact. Measures aimed at reducing the impact of UV radiation include the use of "broad spectrum" sunscreen, wearing sunscreen clothing, avoiding exposure to the sun from 10 to 15 hours, and avoiding tanning beds.
One of the potential sources of exposure to ionizing radiation is medical (X-ray, CT, etc.), and also natural gas radon in the basements of houses. Important prevention strategies include limiting unnecessary CT scans and other diagnostic tests, as well as reducing radiation doses.
Estrogens, female sex hormones, are known carcinogens. Although these hormones play an important physiological role in both women and men, they are also associated with an increased risk of certain types of cancer (breast, endometrial).
Therefore, a woman who is thinking about menopausal hormone therapy should discuss the possible risks and benefits with her doctor.
Studies have also shown that a woman's risk of developing breast cancer may be associated with early menstruation, late onset of menopause, late first pregnancy, or the decision never to give birth, which is also associated with exposure to sex hormones. Childbirth, on the contrary, is a protective factor in this sense.
Certain infectious agents can also cause cancer or increase its risk. For example, human papillomavirus is associated with cervical cancer, hepatitis C virus is associated with liver cancer.
This fact was the basis for the development and implementation of vaccine prophylaxis. In particular, the human papillomavirus vaccine has already demonstrated excellent results in developing immunity to HPV.
Scientists have studied many foods to increase or decrease the risk of cancer. With rare exceptions, these studies have not shown any definitive results on whether eating a particular product contributes to the risk of developing cancer pathology or, on the contrary, prevents this risk.
At the same time, excessive nutrition in general can have a negative impact. Thus, obese people have an increased risk of developing breast, colon, rectum, uterus, esophagus, kidney, pancreas and gallbladder cancers.
Conversely, a healthy diet, physical activity, and maintaining a normal weight can help reduce the risk. Moreover, such "healthy behavior" is also important to reduce the risk of other pathologies, including cardiovascular diseases, diabetes, hypertension and others.
– How to detect the disease at an early stage, what regular examinations should be carried out?
– Screening tests help to detect cancer at an early stage, before symptoms appear. But it's important to remember that when your doctor suggests screening, it doesn't always mean that he thinks you have cancer.
There are different types of screening tests. For example, examining a patient for common signs and symptoms, unusual formations or manifestations, studying his health history, past illnesses and treatment methods.
Screening tests can also be considered laboratory tests of tissue samples, blood, urine or other substances in the body, imaging procedures of internal organs (radiography, ultrasound, CT, etc.) and genetic tests for certain gene mutations.
Each screening test has both advantages and disadvantages. False positive or false negative screening results are also possible.
It is important that patients understand the advantages and disadvantages of screening tests and make an informed choice. Before conducting any examination, it is important to discuss this with your doctor and make a decision together.
– What new opportunities exist in therapy and how does the mortality statistics change?
– New treatment options are far from the only factor that affects mortality statistics. Recently, the results of the observation of cancer indicators and trends in the United States for the period from 1991 to 2016 were published.
Over the course of 25 years, cancer mortality has decreased by 27% with a steady annual drop of about 1.5% since its peak in 1991 (215.1 deaths per 100,000).
The decline in cancer mortality over the past decades in the United States was primarily the result of a steady reduction in smoking, the popularization of a healthy lifestyle, as well as success in early detection and treatment.
The socio-economic situation also has a tremendous impact. Thus, in the United States, residents of low-income counties experience significant problems with the most preventable cancers.
For example, the mortality rate from cervical cancer among women in poor counties in the United States is twice as high as among women in affluent ones. Similar statistics for men: mortality from lung and liver cancer is more than 40% higher among men living in poor districts, compared with the stronger sex in affluent districts.
In Russia, in 2017, 26,506 patients died of cancer (twice as many as in 2005) who were not registered in oncological institutions. The proportion of patients who died within the first year after diagnosis was 22.5%, while with a decrease in the national average in some regions, the dynamics is negative.
All this indicates an unsatisfactory state of diagnosis, including early diagnosis, and still indicates the need to develop and implement an effective national oncological program.
– What is targeted therapy, how does it work? Why does the treatment kill the tumor and not healthy cells?
– Targeted therapy in oncology has proven to be a very effective and promising method of treatment. The basis of this approach is a targeted effect on certain targets, which are endowed with tumor cells.
Targeted drugs are fundamentally different from classical chemotherapy, which is aimed at common biological processes, such as DNA synthesis and mitosis, and "touches" normal healthy tissues and organs.
Unlike targeted chemotherapy, it acts exclusively on the tissue of the neoplasm, practically has no effect on other organs, therefore, the probability of side and toxic effects is minimized, and the effectiveness is comparable and even superior.
– Can neoplasms develop resistance to drugs?
– Maybe. This happens because cancer cells are able to continue mutating, becoming more and more abnormal. At the same time, some mutations make cells resistant to drug treatment.
If this happens, the doctor prescribes a different therapy regimen. Unfortunately, sometimes a tumor develops resistance to many drugs at the same time. Doctors call it multidrug resistance.
– In what cases and why does the cancer return?
– After some time after therapy, the disease may return, for which there are many reasons. One of them is that the initial treatment did not get rid of all the cancer cells and the remaining ones turned into a new tumor.
Some cancer cells could remain after surgery, and some had already broken away from the primary tumor, but were too small to be seen (micrometastases).
Surgeons do everything possible to remove the entire tumor during surgery. But there is always a risk that the cells will remain. Therefore, additional therapy may be recommended, aimed at preventing relapse and controlling micrometastases.
If a patient remains in complete remission for five years or more, some doctors may say that he is cured. In most cancers, relapses occur within the first five years after treatment.
However, some cancer cells may remain in the body for many years after treatment. And there is a risk that the cancer will return later. Therefore, long-term follow-up with a doctor is recommended.
– Is it possible to fully restore the body after treatment?
– Maybe. Every patient is looking forward to the day when the doctor will say that the treatment is finally completed. At this moment, a new important stage begins.
It is necessary to discuss with the doctor the risk of relapse and "late effects" of treatment that may appear several years later, as well as a plan for follow-up, prevention and other important aspects, such as, for example, pregnancy planning.
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