National Cancer Centre of Belarus
Cancer is a disease with poor prognosis. Malignant tumors without early treatment are progressing and result in patient`s death. The most important criterion of prognosis for all malignant tumors is the degree of their spread. Thus, the majority of localized tumor forms not extending the limits organ are completely curable, provided the available up-to-date methods are used. In case of locally advanced tumors extending beyond the organ limits but not involving remote-organs, only part of the patients can be cured. The most of advanced cancer forms are incurable, and therapy is administered to prolong life. Therefore, tumor detection and treatment at early stages before its spreading is the most effective way to decrease malignant tumors mortality rates even if compared to designing of new expensive methods of treatment.
Malignant cancers are not always detected early; as the early forms of tumors are asymptomatics the patient doesn’t feel changes in his/her health and doesn’t consult doctors for examination. To correct the situation, it is proposed to conduct preventive examinations patients without symptoms, and this is what we call screening.
Screening is conducting of population-covering examinations to detect this or that determining malignant tumor in patients without symptoms of this disease. As distinct from screening, the so called early diagnosis is detection of cancer in patients who turn to the doctor with some complaints. The difference in these two approaches is as follows: patients are screened on medical workers`initiative whereas, early detection occurs on their own initiative.
Screening has a number of disadvantages. For instance, in the course screening, cancer is detected in a considerably greater number of patients, compared with routine detection.That is why screening can lead to the so called over-diagnosis associated with detection of small and inactive developing tumors so slowly that they would never be detected and would not cause any problems in the routine practice. As tumor treatment is traumatic, and may result in serious consequences, part of the patients with tumors detected in the course of screening receive "needless" treatment. Another disadvantages of screening are determined imperfect screening tests. A simple and inexpensive method of examination, is usually used as a screening test; however it is not quite accurate, so a positive result requires conformation by a more accurate but also more traumatic method. As a results, part of the patients with a positive result (false positive) are subjected to unnecessary additional examination, while part of the patients with a negative result (false negative) patients do not receive necessary treatment.
In order to make a screening program beneficial and not harmful it is necessary to prove that it significantly decreases cancer mortality rates. It can be proved only by comparing the results of many years of screening with routine detection in two large populations. Many different methods of preventive examination are proposed for early cancer detection. However it turned out that not all of them are beneficial. For instance, regular use of routine lung radiography doesn’t decrease lung cancer, breast palpation doesn’t decrease breast cancer death rates. The efficacy of smear cytology for detecting cervical cancer has been proved, as well as mammography breast cancer, colonoscopy or fecal occult blood analysis for colon cancer.
Screening efficacy has been proved for three malignant neoplasms: cervical cancer, breast cancer, colorectal cancer. Discussions are underway about the need for prostate cancer screening.
In the routine practice, the remaining malignant tumors are detected on the basis of symptoms. In this situation with the development of tumor symptoms, it is important to apply for medical care as early as possible for additional examination. The information about early detection of tumors of different sites can be found in the appropriate items of the Treatment section.
All the above-mentioned recommendations refer to individuals with common risk of cancer development. In case of genetic predisposition to tumor development screening as at an earlier age and on a regular basis. Examination shedules and its multiplicity are determined by a specialist.