- Igor Vladimirovich Pershukov – Doctor of Medical Sciences, Professor, and Doctor of Philosophy (PhD), head of the Department of Hospital Therapy with a course in Radiological Diagnostics and Oncology at Jalal-Abad State University, as well as a fellow of the American College of Cardiology (FACC) and the American Society of Cardiovascular Angiography and Interventions (FSCAI).
Text excerpt:
“One of the key areas of the modern approach to oncology is the primary prevention of malignant tumors aimed at reducing the incidence rate.
It is important to distinguish between individual and state measures for cancer prevention.
Individual prevention
Individual prevention includes informing the population about cancer and adhering to a number of recommendations.
Considering risk factors, every person should remember the following aspects:
- the importance of proper nutrition. It is necessary to exclude pickled and canned products containing nitrites and nitrates. Instead of canning, quick freezing is preferable, which has helped reduce stomach cancer incidence in the USA. It is recommended to limit the intake of animal fats, smoked and fried foods, and to increase the amount of fresh vegetables and fruits in the diet. In conditions of fresh product shortages, taking synthetic vitamins is beneficial. Studies show that vitamins A and E may reduce the frequency of gastric epithelium metaplasia and have a positive effect on precancerous changes in mucous membranes;
- the harm of smoking, both active and passive. Quitting smoking can reduce cancer risk by 30%;
- the influence of endocrine-metabolic disorders. Obesity and frequent abortions increase the likelihood of reproductive system cancer;
- the hereditary forms of cancer. In cases of “familial forms,” it is important to consult a doctor in a timely manner;
- the negative effects of excessive sun exposure;
- the necessity of maintaining oral and genital hygiene;
- the harm of alcohol. Strong alcoholic beverages pose a greater danger, while low-alcohol and medium-alcohol drinks, such as table wines, are less hazardous.
Mass prevention
State measures for primary cancer prevention include monitoring the levels of carcinogenic and radioactive substances in drinking water, food, air, and soil. The state should address environmental issues by developing and implementing filters at polluting enterprises, improving the efficiency of internal combustion engines, using eco-friendly fuels, and eliminating occupational hazards in production.
When malignant tumors are diagnosed at early stages, the chances of complete recovery range from 70% to 100%.
A key element of early diagnosis is screening. The main goal of screening is to reduce mortality from oncological diseases through the active detection and treatment of undiagnosed forms of cancer. Each screening program must meet several mandatory conditions:
- The disease being studied must be socially significant, i.e., with high morbidity and mortality.
- The screening method must have high sensitivity, while specificity is less important.
- The methodology should be accessible to a wide segment of the population.
- It is preferable for the cost and invasiveness of the procedure to be minimal.
- Screening should lead to a reduction in mortality from this disease.
Considering these criteria, several oncological diseases have been selected for which the creation of screening programs is advisable. This includes breast cancer, cervical cancer, stomach cancer, colorectal cancer, prostate cancer, and lung cancer.
However, there are objective barriers to the widespread implementation of screening for these diseases.
For example, the Russian Federation has an approved program for breast cancer screening that includes mammography. According to the program, all women aged 40 to 60 are recommended to undergo mammographic examination every two years in one projection.
However, there are shortcomings in this program. Studies in various countries have shown that the optimal age for mammographic screening is 50-69 years, as the highest number of cases is registered in the age group of 60-64 years. Additionally, mammography should be performed annually and in two projections. For women aged 40-49, mammography can be conducted every two years. The need for screening for women over 70 remains controversial. Studies show that in the age group of 50-69, screening contributes to a 25% reduction in breast cancer mortality. Ultrasound examination of the breasts is not used as a screening method and is only applied for diagnostic clarification. Self-examination as a screening method has been studied in various countries but has not shown a reduction in mortality in groups practicing it compared to control groups. Therefore, self-examination should not be considered an effective method, and women practicing it should be provided with the same recommendations for regular mammography as everyone else. In the USA, due to the development of screening, localized forms of breast cancer (Tis-2N0M0) are diagnosed in almost 90% of women, while in Russia, this figure is only 30%.
Cervical cancer screening began to be widely applied in Scandinavian countries in the 1960s. Cytological examination of smears from the surface of the cervix and the cervical canal (Pap test) significantly reduces mortality from this form of cancer. The effectiveness of screening depends on the interval between tests. Studies have shown that the optimal frequency of examinations is once every three years, which leads to a 90% reduction in mortality. Increasing the frequency to once a year only provides a 1% increase in this indicator. It should be noted that the five-year survival rate for advanced cervical cancer does not exceed 13%, while for localized forms, this figure is 88%. Thus, colposcopic diagnosis, which reduces mortality from cervical cancer, should become a mandatory element of the state preventive measures system.
Stomach cancer screening using esophagogastroduodenoscopy (EGDS) is an effective method for reducing mortality from this disease; however, such results have only been achieved in Japan. In this country, the five-year survival rate for patients with early-stage stomach cancer detected through screening reaches almost 100%. Survival for other stages exceeds 40%, while in other developed countries, this figure does not exceed 20%. Unfortunately, replicating such results in other countries has not yet been successful. Currently, the USA is beginning to implement stomach cancer screening, but results have not yet been obtained.
Colorectal cancer screening is conducted by detecting hidden blood in stool. The effectiveness of this method is confirmed by numerous randomized studies and leads to a 33% reduction in mortality from colorectal cancer with annual testing in individuals over 50. Currently, research is underway on the use of colonoscopy as a screening method, but results have not yet been published. Nevertheless, many insurance companies in the USA are already refusing to renew contracts with individuals over 50 who have not undergone colonoscopy.
For lung cancer screening, chest X-rays (fluorography) and cytological examination of sputum were previously used. Conducted randomized studies did not show a reduction in lung cancer mortality in experimental groups. Thus, fluorography, conducted in Russia in certain groups, is important only for monitoring the situation with tuberculosis and does not increase the level of early lung cancer diagnosis. Currently, the method of low-dose spiral computed tomography (CT) is being tested as a screening method. The use of this method has allowed Japan to diagnose early-stage lung cancer in 80% of patients; however, the cost of this method is a significant limiting factor.
Detection of prostate-specific antigen (PSA) in the blood of men over 50 is actively used for prostate cancer screening. Since the early 1980s in the USA and Europe, due to this method, the incidence of prostate cancer has sharply increased; however, convincing data on reduced mortality is lacking. The increase in incidence is explained by the detection of latent forms of cancer that do not manifest clinically, do not progress, and do not lead to death. Such cancer does not affect the patient's life expectancy or quality of life, and aggressive treatment can sometimes worsen the condition. In this regard, many specialists prefer a watchful waiting strategy, where patients are regularly monitored, and treatment begins only with disease progression.
Thus, the effectiveness of screening has been proven for:
- breast cancer through mammography in women aged 50-69;
- precancerous conditions and cervical cancer through colposcopic diagnosis;
- precancerous conditions and colorectal cancer through hidden blood testing.
The effectiveness of screening for the following diseases is under study:
- prostate cancer through PSA testing;
- breast cancer in women under 50;
- stomach cancer through EGDS;
- lung cancer through spiral CT;
- some other methods.
The insufficient effectiveness of breast self-examination and chest X-ray as screening methods for cancer has been confirmed.
To improve the quality of early diagnosis and reduce mortality from oncological diseases, it is important not only to create screening programs but also to prepare specialists, engage broad segments of the population (including personal invitations), actively promote in the media, and monitor all stages of the program with an assessment of its effectiveness. In the implementation of national screening, involving 60% of the target audience is considered minimally effective. In Scandinavian countries, the coverage of the population in breast and cervical cancer screening reaches 90% or more, while in Russia, this figure, unfortunately, does not exceed 20%.
The key role in the timely diagnosis of malignant tumors is played by the population's “oncological alertness” and the literacy of doctors, especially at the primary level. It is necessary to actively disseminate information about preventive examinations and early symptoms of malignant diseases. Unfortunately, the professional skills of medical personnel are often insufficient, which leads to many advanced cases of the disease being identified for the first time. A significant contribution to late diagnosis and unsatisfactory treatment outcomes is made by the alternative treatment methods that have become widespread in recent years, which are not always applied by oncology specialists and are sometimes even conducted by individuals without medical education.”
