Screening and early detection of cancer. To whom and when are they appointed? What is a screening examination

Cancer screening is the search for a malignant growth in a person who does not have any symptoms of a tumor. In some cases, such tests help to detect diseases on early stage when many types of cancer can be completely cured. The appearance of complaints in a patient may indicate the growth and spread of a malignant neoplasm, and, consequently, a worsening prognosis for the patient. Screening studies can reduce cancer mortality.

Screening test options

• medical survey (questionnaire) and examination
• laboratory tests(examination of tissues, urine, blood, feces)
• medical imaging techniques (examinations that allow you to get a picture internal organs)
• genetic studies aimed at identifying mutations that can lead to the development of tumors

Cons and risks of screening studies

Screening does not always help detect cancer in the early stages, and many tests have a chance of any complications. It is important to know, firstly, whether the study has proven efficacy in reducing cancer mortality, and secondly, to be aware of the possible risks in conducting it.

For example, colonoscopy or sigmoidoscopy are performed as screening for colon cancer, but these are serious and unpleasant medical studies for the patient, in which, in particular, damage to the intestinal mucosa and bleeding are possible.

Screening sometimes gives false positive result, i.e. the test shows that there is cancer, and after additional studies, the tumor is not detected. At the same time, medical procedures are prescribed for a detailed examination, which lead to understandable feelings on the part of a person and his relatives, are often expensive and can cause complications in themselves.

A false negative result is also possible, i.e. the test result is normal, but meanwhile there is cancer. In this case, people often postpone a detailed examination, even when symptoms appear.

In some cases, the detection of cancer as a result of screening does not prolong or improve the life of the person examined. There are types of cancers that rarely threaten the patient's life or are almost not accompanied by any complaints. But if the cancer is found as a result of the test, they begin to treat it. There is no way to establish exactly whether the therapy started in such cases prolongs the life of the patient or not. On the other hand, an increased number of suicides among adolescents and adults during the first year after a cancer diagnosis is known. Yes, and in the treatment of cancer, the development of severe side effects and serious psychological problems. So in certain cases, an accurate diagnosis and treatment does not increase the likelihood of a cure.

It is better to make a decision about participating in a screening program after analyzing detailed information about both the tests themselves and what their result will give to a particular person. And it is necessary to compare the expected benefits of early diagnosis of the tumor and the potential risks of overdiagnosis and retreatment.

Goals of screening programs

The ideal test should:

1. Find the tumor before any symptoms appear
2. Detect those cancers that respond well to therapy when diagnosed at an early stage
3. Do not give false positive and false negative results
4. Reduce cancer deaths.

Screening tests do not diagnose cancer. If the test result does not correspond to the norm, then additional examinations are carried out, up to a biopsy for an accurate diagnosis.

Some screening tests are designed to identify a person's risk factors for certain types of cancer. Their presence does not mean that the tumor will definitely grow, just as their absence does not mean that there will be no oncological pathology.

There are studies only for those people who have risk factors for cancer:

• past diagnosis of malignancy
• diagnosis of cancer in two or more blood relatives
• certain gene mutations associated with cancer.

For risk groups, screening studies are carried out more often or begin to be carried out at more early age. One of the tasks is to identify new risk groups for various types pathology.

National screening programs differ depending on the level of medical development and economic opportunities, as well as data on morbidity and mortality. Tests change over time as new methods have higher performance.

List of studies proven to reduce cancer deaths

(according to National Cancer Institute, USA)

Colonoscopy, sigmoidoscopy and highly sensitive methods for detecting blood in the stool- for colon cancer. During colonoscopy and sigmoidoscopy, the doctor is able to detect intestinal polyps and remove them before they degenerate into a cancerous tumor. Usually, endoscopic examinations of the intestine are recommended as screening at the age of 50 to 70 years.

Low-dose spiral lung tomography used as a screening test for heavy smokers aged 55 to 74 years.

Mammography carried out in women aged 40 to 74 years for the early detection of breast cancer. The method significantly reduces mortality from this disease, especially in the group older than 50 years.

Pap test and human papillomavirus tests reduce the incidence of cervical cancer, as atypical cells are detected before tumor development. Mortality from this pathology is steadily declining. These studies are recommended to be carried out regularly, from the age of 21 to 64 years.

Other screening tests

Determination of alpha-fetoprotein in the blood, together with ultrasound of the liver, is used as a screening for liver cancer at a high risk of developing it.

MRI of the mammary glands used for mutations in the BRCA1 or BRCA2 genes. This group has a very high risk of breast cancer and some other malignant neoplasms.

Determination of tumor marker CA-125 in the blood is often done together with transvaginal ultrasound of the female genital organs for early detection of ovarian cancer, especially at an increased risk of this disease.

Breast self-examination and medical examination of the breast do not reduce mortality from breast cancer. Of course, when a formation is detected in the mammary gland, it is necessary full examination to make a diagnosis.

Blood test for PSA marker together with a digital rectal examination of the prostate gland allows you to detect a prostate tumor at an early stage.

Carry out regularly skin examination often recommended for people at high risk of skin cancer. Although such self-examination does not reduce mortality from malignant neoplasms of the skin and sometimes leads to overdiagnosis, changes in the shape and color of moles, the appearance of new or ulcerations on the skin is a reason to see a doctor.

Transvaginal ultrasound allows you to get an image of the ovaries and uterus, which is important for women with an increased risk of ovarian cancer (with a BRCA1 or BRCA2 mutation) or endometrial cancer (with Lynch syndrome).

Early detection of malignant tumors is very important to reduce mortality, and if precancer is detected, morbidity.

The purpose of screening is to identify among a healthy population of individuals at high risk of any pathology. Screening diagnostics is aimed at detecting a specific disease and is a rather expensive process, so it is not widely prescribed. The value of effective screening diagnostics lies in its relative ease of implementation, low cost, and ability to exclude the vast majority of individuals who are not at high risk for the pathology that this diagnostic was aimed at identifying. That is, only a small number of people who have been screened need more expensive clinical and laboratory research, with which you can exclude or confirm a specific pathology.

Screening is useful in cases where early detection of pathology contributes to a more favorable outcome. That is, if effective treatment there is no specific pathology or early treatment will not be beneficial, the value of information about the presence of a pathology will be rather doubtful, and in some cases it may even be harmful.

The ethical aspect of disease screening should also be noted. The fact is that persons who do not suffer from specific pathologies (as a rule, the majority of them) must undergo a procedure that will in no way have a direct impact on the state (improvement) of their health and well-being. And those patients in whom the screening analysis showed a positive result should undergo additional, more thorough diagnostics. In this case, information about a possible illness (or a high risk of illness) often becomes a cause of anxiety and stress. Despite this, any screening brings more benefits to people with a detected pathology, which far outweighs the potential harm brought by healthy people.

No screening can be considered completely reliable. There are many reasons that can be influenced, and which cannot. Therefore, the results screening studies may be positive in healthy individuals and negative in patients. And both of these options can provide Negative consequences Therefore, national screening programs are constantly updated, relying on the results of modern research, thus minimizing the number of false negatives and false positives.

Undoubtedly, the high cost of screening programs and a number of other reasons significantly limit their use. Today, in many economically developed countries, only a small list of pathologies is screened, despite the fact that over the past few years this list has increased and its further expansion is the subject of close attention. Table 1 provides a list of national screening programs in use in the UK.

Implementation of the screening method.

Screening - conducting simple and safe studies of large population groups in order to identify risk groups for the development of a particular pathology.

This method is very important and allows to identify various pathologies in the prenatal and neonatal periods, to achieve a decrease in the frequency of detection of common forms, an increase in the frequency of detection of early forms of cancer and an improvement in survival.

Prenatal screening - studies conducted by pregnant women in order to identify risk groups for pregnancy complications. Prenatal screening usually includes ultrasound and biochemical screening. According to the gestational age, screening of the first and second trimester is distinguished. Neonatal screening - mass examination of newborns for the most frequent congenital diseases. A drop of blood from the heel is taken from each newborn on a special test form, which is sent to the medical genetic consultation for research. If a disease marker is found in the blood, parents with a newborn child are invited to a medical genetic consultation for a second blood test to confirm the diagnosis and prescribe treatment. In the future, dynamic monitoring of the child is carried out. Neonatal screening allows early detection of hereditary diseases and their timely treatment stop the development of severe manifestations of diseases leading to disability. Neonatal screening can prevent complications of such diseases as hypothyroidism, phenylketonuria, cystic fibrosis, galactosemia, adrenogenital syndrome.

Screening methods also include laboratory tests that allow you to determine the types of various infectious pathogens, ultrasound research methods, tomography, PCR, ELISA and many other tests.

The purpose of screening is high quality detection of pathology, but there are a number of problems here. False-positive and false-negative conclusions are a serious problem.

For a sufficient level of screening tests to be performed, a number of conditions must be met:

1. Informing the population about screening.

2. Providing reliable and high-quality accounting, storage and reproduction of information.

3. Principles of questioning the population. At the moment, a questionnaire has been created in Ukraine, which includes 20 questions. However, the answers cannot be used to make a decision in medicine, as they contain only the personal impressions of the respondents and do not coincide with the conclusions of qualified doctors.

4. Evaluation of any type of screening according to the criterion "medical efficiency-cost".

5. An important issue is the decision of who can evaluate the results and in whose interests the screening is carried out.

When a woman is expecting a baby, she has to take multiple tests and undergo scheduled examinations. Each expectant mother may be given different recommendations. The screening test is the same for everyone. It is about him that will be discussed in this article.

Screening study

This analysis is assigned to all expectant mothers, regardless of age and social status. Screening examination is carried out three times during the entire pregnancy. In this case, it is necessary to observe certain deadlines for the delivery of tests.

Screening research methods are known to medicine, which are divided into two types. The first of these is analysis. It determines the possibility of various pathologies in the fetus. The second analysis is an ultrasound screening study. The evaluation should take into account the results of both methods.

What diseases does the analysis reveal?

Screening during pregnancy is not an accurate way to make a diagnosis. This analysis can only reveal the predisposition and establish the percentage of risk. To obtain a more detailed result, it is necessary to conduct a screening study of the fetus. It is assigned only when the risks possible pathology very high. So, this analysis can reveal the possibility of the following diseases:

During the examination, the doctor measures the growth of the fetus, notes the location of the placenta. Also, the doctor must make sure that the child has all the limbs. One of the important points is the presence of the nasal bone and It is on these points that the doctor will subsequently rely when deciphering the result.

Second survey

Screening during pregnancy in this case is also carried out in two ways. First, a woman needs to take a blood test from a vein and only after that undergo an ultrasound scan. It is worth noting that the established terms for this diagnosis are somewhat different.

Blood test for second screening

In some regions of the country they do not conduct at all this study. The only exceptions are those women whose first analysis gave disappointing results. In this case, the most favorable time for blood donation is in the range from 16 to 18 weeks of fetal development.

The test is carried out in the same way as in the first case. The computer processes the data and produces the result.

Ultrasound examination

This examination is recommended for a period of 20 to 22 weeks. It is worth noting that, unlike a blood test, this study is carried out in all medical institutions in the country. At this stage, the height and weight of the fetus are measured. The doctor also examines the organs: the heart, brain, stomach of the unborn baby. The specialist counts the fingers and toes of the crumbs. It is also very important to note the condition of the placenta and cervix. In addition, dopplerography can be performed. During this examination, the doctor monitors the blood flow and notes possible defects.

During the second ultrasound screening, it is necessary to inspect the water. They should be normal for a given period of time. Inside the fetal membranes there should be no suspensions and impurities.

Third survey

This type of diagnosis is carried out after the most suitable period is 32-34 weeks. It is worth noting that at this stage, blood is no longer examined for defects, but only ultrasound diagnostics are performed.

During the manipulation, the doctor carefully examines the organs of the future baby and notes their features. The height and weight of the baby is also measured. An important point is the normal physical activity during the study. The specialist notes the amount of amniotic fluid and its purity. Be sure to indicate the condition, location and maturity of the placenta in the protocol.

This ultrasound in most cases is the last. Only in some cases, re-diagnosis is prescribed before childbirth. That is why it is so important to note the position of the fetus (head or pelvic) and the absence of cord entanglement.

Deviations from the norm

If during the examination various deviations and errors were revealed, the doctor recommends that a geneticist be seen. At the appointment, the specialist must take into account all the data (ultrasound, blood and pregnancy features) when making a specific diagnosis.

In most cases, the possible risks are not a guarantee that the child will be born sick. Often such studies are erroneous, but despite this, doctors may recommend additional studies.

A more detailed analysis is a screening study of the microflora of the amniotic fluid or blood from the umbilical cord. It should be noted that this analysis entails negative consequences. Quite often, after such a study, every woman has the right to refuse such a diagnosis, but in this case, all responsibility falls on her shoulders. If poor results are confirmed, doctors suggest abortion and give the woman time to make a decision.

Conclusion

A screening test during pregnancy is a very important test. However, we must not forget that it is not always accurate.

After birth, the baby will undergo neonatal screening, which will absolutely accurately show the presence or absence of any disease.

Screening consists in the systematic, population-wide, application of any research method in people without symptoms of the disease, but at a sufficiently high risk of developing it, in order to form a group for further examination or targeted prevention. In other words, screening is the application diagnostic methods asymptomatic individuals in order to divide them into two groups: those who would benefit from early intervention and those who would not.

What does an effective screening program include?

Screening program eligibility criteria

Disease

• The disease must represent an important medical problem.
• The natural course of the disease (including from asymptomatic to clinically pronounced form) should be studied.
• The disease must have a latent but recognizable or clinically apparent early stage.

Screening method

• There should be the most appropriate method of examination, with sufficient specificity and sensitivity.
• Screening should be continuous.
• Screening examination methods should be acceptable to the group of people in which it is planned to be used.

Follow-up interventions

• All conditions for the diagnosis and treatment of diseases should be created.
• A recognized effective method treatment of diseases.
• Generally accepted protocols should be used that specify who needs to be treated.

Price

• The cost of screening (including the diagnosis and treatment of detected cases) should be balanced by the total cost of treatment.

The most important principle of any screening program is that in order to reduce morbidity and mortality, early detection should be carried out with the aim of the earliest possible intervention. If there is no improvement in outcomes, the point of screening is lost. Early diagnosis by itself does not justify screening. the only justification for a screening program is early diagnosis leading to effective improvement in outcome.

Principles

Randomized trials of the feasibility of population screening have convincingly shown that early detection of cancer improves the patient's chances of a cure. This became the basis for a broad public outreach aimed at raising public awareness of cancer in order to encourage those who have identified suspicious symptoms to seek medical attention in a timely manner. However, there is still no reliable evidence that the early referral strategy medical care increased the survival rate of cancer patients.

Screening is a mass screening of non-complainers to detect a tumor that is not yet clinically manifest. For screening to be effective, it is necessary that the disease meet certain criteria, that screening studies be selected and that a screening program be drawn up.

Criteria

• The disease can be diagnosed at an early stage.
• Treatment of the disease at an early stage is more effective than in the later stages.
• The disease is sufficiently common in the study population to justify screening.

Screening studies must meet the following requirements:

• sensitivity and specificity;
• ease;
• safety;
• relative cheapness.

Program

• Availability of the necessary equipment to clarify the diagnosis with a positive result of screening studies.
• The possibility of qualified treatment for those who have a disease.
• Repetition of screening studies at regular intervals if the disease begins insidiously.
• The benefits of the examination should outweigh the physical and psychological discomfort it causes.
• The benefits of the survey must justify the material costs.

It is important that the results of treatment of the disease at an early stage are better than in the later stages. It is incorrect to judge the effectiveness of the screening program by comparing the outcome of a disease detected during screening and at the clinical stage, since the following three factors make such a comparison inadequate (in favor of a screening study).

• Lead interval. With early detection of a disease by screening, the period from diagnosis to death is lengthened, regardless of whether treatment has altered the natural course of the disease or not. If a patient dies of cancer at the same age that death would have occurred without screening, then screening is useless. Screening is only worthwhile if screening patients have a higher survival rate than non-screened patients.
• Difference in malignant potential of tumors. On screening, slow-growing tumors are more likely to be detected than tumors that differ rapid growth and more often manifest clinically before a screening study is performed, or in the interval between screening studies. Thus, tumors detected by screening are characterized by a lower malignant potential and a relatively more favorable prognosis.
• Sample deviation. This factor is due to the characteristics of patients agreeing to undergo screening. Unlike people who refuse to participate in screening or ignore it, they often have a number of health characteristics, so regardless of the course of the tumor process, they live longer.

Screening

When conducting screening, it is important to design the sample so that useless tests are not performed on individuals with low cancer risk. Thus, when screening for the detection of common malignant tumors, the frequency of which increases with age, the study group includes individuals of an age at which this tumor is encountered quite often and when radical treatment is possible.

About risk malignant tumor can be judged by other factors. Great importance in this regard, has a family history, especially given the now emerging opportunities to identify specific gene mutations by examining the patient's blood. Knowledge of these mutations allows close relatives of the patient to be screened. Examples include mutations in the APC gene in familial adenomatous polyposis of the colon, mutations in genes involved in DNA mismatch repair in hereditary colon cancer without polyposis, and mutations in the BRCA1 and BRCA2 genes in familial breast and ovarian cancer.

The screening test should be easy, safe and acceptable to patients. It must also be sensitive and specific. Sensitivity characterizes the proportion of patients with a given disease in whom the study gave a positive result, and specificity characterizes the proportion healthy patients who tested negative.

Screening program

Once a screening program has been approved, it is important to provide the necessary diagnostic equipment as well as treatment options to minimize morbidity and mortality.

It should also be remembered that screening can cause psychological trauma to the patient, which, together with the somatic complications associated with the study and treatment, is part of the cost of screening. The benefits of early cancer detection must outweigh these costs, and society must decide whether the benefits are worth the expense.

Randomized trials in breast and colon cancer have shown that screening can significantly reduce mortality in both cases. For breast cancer, mammography was chosen as a screening study, its informativeness significantly depended not only on the quality of the images, but also on their interpretation. In colon cancer, the screening study consisted of fecal analysis for occult blood followed by a colonoscopy if the result of the analysis was positive.

The screening program for early detection of breast cancer has included mammograms every 3 years since 1986 for women aged 50 to 64 years. The upper limit of age by 2007 will be changed to 70 years.

Sexually active women aged 21 and older were included in screening for early detection of cervical cancer by family physicians in the UK. Investigated smears from the cervix. Although the study was not controlled, the reduction in mortality from cervical cancer is largely attributed to screening. In the UK, cervical smear screening is done every 1-3 years.

Screening for early detection of colon cancer

In 2005, after several studies supporting screening for the prevention and treatment of colon cancer, the UK government supported the program. However, it will take time, material and human resources to mass-produce colonoscopy as envisaged by this program. Calculations showed that the program would cost £20,000 for each year of life saved.

New non-invasive examination methods using CT are being developed, such as virtual colonoscopy. In experienced hands, they can detect tumors no larger than 5 mm. However, these methods are not yet available. In 5-10 years, they, apparently, can already be used in screening studies.