According to forecasts of the world health organization (WHO), the incidence and mortality of cancer worldwide will increase in 2 times for period from 1999 year for 2020: from 10 to 20 million new cases and from 6 to 12 million registered deaths.
In developed countries there is a tendency to deceleration of growth of morbidity and mortality from malignant tumors (both at the expense of prevention, first and foremost the fight against Smoking, and by improving early diagnosis and treatment) due to high-quality cancer treatment in cancer clinics.
Factors external and internal environment that may be causes of tumors and contribute to their development, are called carcinogenic. Modern science is actively studying them.
According to the Committee for the prevention of cancer of the who, 90% of tumors associated with exposure to external factors, and 10% depend on genetic factors and viruses. But this opinion is very controversial.
The Most extensive group of tumors are the so-called “spontaneous” cancers of unknown etiology that occurs outside the explicit dependence on viral oncogenic or other external factors.
The basis of occurrence of tumors is the emergence and multiplication in the body the tumor cells capable of transferring acquired properties in an infinite number of generations. Therefore, tumor cells are considered as genetically modified. The growth of the tumor gives one single cell, its division and division occurs when new cells – the main method of tumor growth. The migration and proliferation of tumor cells in other organs and tissues leads to the formation of metastases.
Main Causes of Cancer
Thus we see two factors in the occurrence of tumors: the occurrence of altered cells and the conditions for its unhindered growth and reproduction in the body.
In all tissues (especially epithelial cancers of which there are up to 90% of malignant tumors), there is a constant division, the formation of new cells instead of dying. In an endless cycle of updates inevitably errors, “cell marriage” on the visible and invisible reason to us. It occurs in all living creatures, and humans in particular, many times daily. Of course, the more cycles of cell division took place, the greater the likelihood of a “defective” cells in its “offspring”. This explains the sharp increase of the probability of occurrence of cancer with age for most cancers. More than 50% of all cancer cases are detected in people aged B5 years and over. Statistics show that if we take the death rate from cancer in the age of 20 per unit, 50-59 years, the risk of dying from this disease will increase in 50 times, and 60 years and older the likelihood of this will increase even more: for men and 119 for women — in 78 times.
The body has special mechanisms for recognition and destruction of such a “marriage” of cells, which is essentially foreign to the body. The body fights with them as well as cells released from the outside (bacteria or transplanted organs) by using the immune system. But in a “perfect” day immune system fails, for whatever reasons understudied miss “defective” cell, capable of continuous reproduction and uncontrolled growth.
In all probability it was the violation of the immune system are crucial in the development of tumors, since the appearance of cell defect is inevitable, and it all depends on how smoothly and efficiently it is recognized and promptly destroyed.
Conception of the role of immune mechanisms in development of malignant neoplasms was first put forward in 1909 by Ehrlich and later extended by many researchers. Studies in recent years have confirmed the significant value of the factor of immunosuppression in the development of tumors. The role of immune system disorders the development of malignant tumors is confirmed by the more frequent development of tumors in disorders of immunological control in the body (immunodeficiency syndromes – agammaglobulinemia, ataxia-telangiectasia, etc.; long-term use of immunosuppressive in the case of organ transplantation and in some diseases). Such patients require more frequent medical monitoring for the timely detection of the tumor.
The following internal and external factors are also considered carcinogenic, as they can affect the above-mentioned natural processes of formation and destruction of the changed cells. But their importance is secondary.
In the more adverse conditions is the cell, the greater the likelihood of errors during its division. Trauma to the skin, mucous membranes or other tissues of the body by any mechanical or chemical stimuli leading to increased risk of occurrence of tumours in this location. This is what determines the increased proportion of cancer of those organs, mucosa which are exposed to the most intense natural load: lung cancer, stomach, colon etc. Irritation of the bronchial mucosa by tobacco smoke, the mucosa of the esophagus and gelule rough and spicy food, injury the dense feces of the ampoule of the rectum and anus, etc. leads to a precancerous disease and further increases the risk of cancer. Constantly traumatized moles or scars, indolent ulceration also lead to intense cell division under adverse conditions and increase this risk.
In adverse conditions fall and cells of internal organs, the function of which is impaired due to various internal and external factors. This is most evident in hormone-dependent organs and glands of internal secretion. This leads to an increased risk of breast cancer, uterus and ovaries in women, prostate in men, etc. Often this becomes the main reason in the development of tumors in young patients.
In the development of some tumors important are genetic factors. In animals, the role of genetic predisposition is obvious (for example, high – and nizoralnyh lines of mice). In humans, the tumor may be the only manifestation of the defect genes, and various genetic disorders resulting in multiple malformations and tumors. Such family members must be under special surveillance by oncologists for early detection of the tumor. They need to be very careful when choosing a professional activities (necessary to avoid contact with potential carcinogens). Among the known “genetic” tumors – retinoblastoma, newusa basal cell carcinoma, trichoepithelioma, multiple endocrine adenomatosis, pheochromocytoma, medullary thyroid cancer, paraganglioma, polyposis of the colon.
External carcinogenic factors can be schematically divided into three main groups:
The principle of action of external carcinogenic factors on a cell is not completely understood. Hence, there is no possibility of obtaining convincing evidence of their carcinogenic effect on the human body, with the exception that analytical epidemiological studies.
Science is known, mainly in animal experiments, a large number of chemicals that can be carcinogenic. It will nalezhat aromatic carbohydrates (benzpyrene, benzanthracene), aromatic amines (aniline dyes – naphthylamine), nitrogenous compounds, pesticides (herbicides, insecticides, fertilizers, flavonoidi, asbestos, etc. the Source of most of the carcinogens in the environment are emissions from industrial production. Via contaminated soil, water, air, biological organisms, carcinogens are absorbed by the skin, lungs and food in the body. Carcinogens produced by burning tobacco and is inhaled while Smoking.
Physical factors deserve special attention, different types of radiation. As a result of nuclear tests, accidents at nuclear power plants, nuclear ships and submarines, the expansion of human activities involving the use of radiation sources, large scale spread of acquired radionuclides. They can get into the body with drinking water, food. And since the half-life of the major radioactive elements (cobalt, cesium, strontium) is calculated for decades, the pathogenic effect in the body chronic, dolgoletie. Besides it should be added that due to the reduction of the ozone layer of the Earth’s atmosphere and the emergence of the so-called “ozone holes” increases the flow and activity of the ultraviolet rays of the Sun.
In latest time available to the General population literature provides data on the possible viral nature of malignant tumors. That Is disturbing and of concern to many.
The Role of viruses in the development of human tumours remains controversial. Facts which undoubtedly would have testified about the oncogenic role of viruses in the most common tumors of man, not received. In animal experiments, some forms of tumors associated with viruses. Perhaps to biological carcinogens prinalezhit the hepatitis b virus, herpetophobia virus, adenovirus, HIV virus, as well as the products of certain fungi (aflatoxins), parasites (cat diuretic). With the help of molecular biology techniques in the above oncovirus was revealed transforming genes are called oncogenes. Normal oncogenes are present in all cells of the human body (they regulate the growth, division and differentiation of cells). Perhaps under the influence of different factors (growth factors, chemical and physical carcinogens) the activation of oncogenes and, as a result, continuous “uncontrolled division of cells is the main symptom of the degeneration of cells.
The Viral nature of the disease does not mean it is contagious. Viruses that are considered a cause of some tumors in animals, are not transmitted by contact from a sick animal healthy. None of the patients with cancer of the lip did not get sick the family cancer throughout the time of observation of patients with cervical cancer was not a single case of cancer of the penis in their spouse. Such cases are not described in the literature. Despite the ease of proof of nezaleznosti cancer, many doubters.
Evidence of cancer independent enough. The story of the struggle with malignant tumors, the observations of scientists and surgeons patients, and experimental studies convincingly prove independent cancer. Not only surgeons, but also directly serving cancer patients, medical personnel do not become infected. The incidence of cancer among these occupations does not exceed the incidence of persons in contact with patients.
At the European cancer conference held in Vienna, Dr. R. Peto (UK) presented the report on the main causes of cancer:
During the 90s every year from cancer in the world died 8 million people. The most common forms of malignant tumors were lung cancer (1.3 million-16%), stomach (1.0 million of 12.5%), upper digestive tract (0.9 million-11%, mainly due to cancer of the esophagus), liver cancer (0.7 million-9%). The major causes of cancer of the lung, mouth, larynx, and in some cases the esophagus and stomach according to the reporter is Smoking, while hepatitis B is a major cause of liver cancer. Methods of early diagnosis and treatment of these disorders is unsatisfactory. Therefore, the Rapporteur proposes to focus on prevention. Smoking cessation and vaccination against hepatitis b was capable, in his opinion, significantly reduce the incidence and therefore the mortality of lung cancer, upper respiratory tract and liver.
4 million deaths due to colon cancer (0.6 million 7,5%), breast cancer (0.4 million-5%), prostate (0.3 million-4%), cervical (0.3 million-4%), pancreas (0.2 million-2.5%) and bladder (0.2 million 2,5%). The main reasons for these diseases are referred to as hormonal disorders (breast cancer and prostate cancer), human papilloma viruses (cervical cancer), Smoking (cancer of the pancreas and bladder). Therefore, Smoking is responsible for 20% of all deaths from malignant tumors. Other causes Rapporteur called viral infection (hepatitis b virus, papillomavirus, Epstein-Barr, etc.), dietary factors, environmental pollution, exposure to the sun.
If you agree with the speaker, we have with sorrow to admit that all of the above causes of cancer we have a tendency to increase. Unlike the rest of the world, where the anti-Smoking struggle, and our country thrives and propagated the cult of Smoking. There is a growing incidence of hepatitis b virus, there is no prevention of HPV, which is sexually transmitted, deteriorating quality of food the majority of the population in connection with economic difficulties, rising environmental pollution and negative influence of technogenic factors on human.
But more important is that we have no anti-cancer program, is also the prevention of cancer and medical examination of the population, is not carried out early diagnosis of precancerous and tumorous diseases, the worsening of the situation with the organization of medical care. All this inevitably leads to increased morbidity and mortality from malignant neoplasms.