Klin Onkol 1999; 12(Suppl 2 1999): 3-5.
SUMMARY
Malignant tumours represent a serious political and social problem which requires the introduction of complex cancer programs. These programs have to be based on valid data. Cancer registries as organizations dealing with the systematic collection, storage, analysis, interpretation and presentation of information about various forms of cancer are one of the most important sources of such information. The cancer registration process is coordinated on the intemational level. According to the purpose, they are population based, hospital-based, or based on other specific needs.
The data from the National Cancer Registry of the Czech Republic (NCR), with its more than 1 million registered cases of newly diagnosed malignant tumours from the years 1976-1998, constitutes a valuable information database with increasing importance and exploitation possibilities. The need of for organisation and introduction of a system and quality assurance of care for cancer patients in our republic required the introduction of mandatory recording of tumour diseases as early as in the year 1951. The registration of malignant tumours serves as assurance of statistical evidence about malignancies; it also provided expert support of diagnostic and treatment practice and follow-up. The collection, control and preliminary data processing is carried out by a network of district and regional offices of the NCR by highly qualified registry staff. The NCR data is centralised by the national office, working within the framework of the Institute of Health Information and Statistics of the Czech Republic, which participates together with the Board of NCR on the organisation and methodological guaranty of the registration. The district and regional NCR offices use unified hardware and software equipment, specialised for this purpose. Besides periodicaly processed and published basic overviews, the NCR data is specifically processed to cover the needs of the health care organisation and for research purposes. The legislative requirements for the protection of persona1 data of registered patients are fulfilled during the service and exploitation of NCR data. Presently, emphasis is given to the preservation of reporting quality and on quality standardization of the obtained and proces sed data according to the requirements of Intemational Association of Cancer Registries (IACR).
The need to evaluate results of the scientific activity, health care, interdisciplinary and intemational cooperation requires precise classification and coding of diseases. Basic characteristics of malignant tumours anatomical site, histological type, biological behaviour and extent of disease are described according to the classification systems ICD, ICD-O and TNM. The classification systems are continuously innovated and complemented. Efficient use of the classifications requires good knowledge of the classification criteria.
The Cancer Reporting Forms are a transparent source of information about newly diagnosed malignant tumour in every registry. The extent of monitored data is controlled by IACR recommendation and is adapted for local conditions and needs of particular countries. The extended version of the Cancer Reporting Form and Follow-up Report will be introduced in the Czech Republic starting January 1, 2000 as a response to the increasing necessity for international standardization and also to the current requirements of health care control and epidemiological needs.
High-quality cancer registries are necessary for the effective management of cancer control programs. Basic criteria for the quality of the registry are the completeness, accuracy, integrity and international comparability of existing data. Standard quality of the registry requires a complex approach in all areas of cancer registration, i.e.: definition of goals, methodical prerequisites, exploitation of data and marketing, staff resources, software and hardware equipment, legislative and economical conditions. Audit studies are an acknowledged tool for verification of registry quality. Executed audit studies of NCR activities confirmed its stable quality, comparable with reputable foreign registries. They called attention to the importance of the functioning of NCR district offices and also to the need to carry out specific actions in the methodical and educational field.
Death Certificates (DC' s) are an important source of information for NCR. Their quality is often taken as dubious. Therefore an audit study was carried out, aimed towards the verification of DC and as control for the completeness of NCR by means of comparing with DC. There have been 3517 DC's from nine district offices (DO NCR) included into the study. The processing consisted of comparison of every DC with the data in the NCR database and with available health records. The results showed the relatively good quality of data in DC's and confirmed the need for regular processing of DC 's in DO NCR. This type of study is not cost consuming and is recommended as an audit study for the precision and completeness of NCR and also for the quality of work in DO NCR.
The experience of particular DO NCR indicates varying quality of the obtained basic documents and an increasing need for active search for health records and completion of delivered Cancer Reporting Forms. This fact led to the implementation of an audit study, aimed towards quality monitoring of NCR background information. All documentation routinely processed at 10 NCR district offices during three months was included into the study. The processing of 6725 records related to 2259 newly reported cases of malignant tumours included evaluation of the quality of delivered reporting forms, the dare of delivery, and the possible need for a reminder was also recorded for every document. The study confirmed empirically known facts about the crucial role of DO NCR in tracking records and completion of reporting forms. It found differences in the system of processing in the DO NCR included into the study. The results indicated the necessity of structured methodical and training activities of the NCR. The utilized routine can be recommended for regular implementation in the scope of audit studies of NCR quality.
The mortality/incidence ratio (M:I) is one of the internationally respected parameters of registry quality, characterising the completeness of registry. The study of the M:I parameter included comparison of data from the Czech Republic (CR), with foreign data, historical development in the CR and also the evaluation of this parameter at the district level. The study, covering the period 1983 1994, confirmed the stability of NCR and its completeness, comparable with respectable foreign registries. Analysis on the district level showed some difficulties in non-uniform registration of the causes of death, and the necessity of methodical and training provisions stemming from this discrepancy. The study confirmed the efficiency of exploitation of the M:I parameter for audit studies of NCR quality.
The completeness of the registry can be verified by its comparison with independent sources of information. The audit study, using this principle, was carried out, comparing the NCR data with histopathological findings (HPF), as independent sources of information processed in DO NCR. 8337 records of positive HPF, delivered to DO NCR Brno-City, was included into the study. The conclusions confirmed well-accepted facts, i.e. differences in the observance of reporting by various districts, medical specialisation or medical facilities, and reporting duty to the necessity to carry out structured methodological provisions for improving the report quality. This study cannot be recommended as an audit method for high elaborateness.
Great amount of information has been collected in cancer registries during long years of activity. The procedures for their processing, presentation and exploitation are a subject of international standardization and demand experienced experts and interdisciplinary cooperation. Registry data can be used in a broad variety of fields on an individual or general basis. General data is possible to present in the form of tables, graphs or maps. The processing requires qualified interpretation and protection of individual data. Cancer registry information can be obtained from yearbooks or specialised monographs, as specially solicited outputs or by personal processing from the provided data. An overview of the most important publications of cancer registries on the international or domestic level is shown in references.
Data about the numbers of newly diagnosed cases, about all surviving patients, and about the number of deaths is a basic parameter of cancer epidemiology. It is exploited by several means as absolute, proportional and standardized values. Every mentioned possibility serves for other purposes, and has its advantages and drawbacks. Mutual relations between the above mentioned parameters in long-term time series indicate the level and changes (positive and negative) in health and diagnostic care. Information about less frequently used parameters can be obtained from mentioned references.
The frequency of breast cancer in women is serious problem. The study based on the NCR data for the Southern Moravia region showed a long-term stabilized, statistically significant increase in incidence, a shift of newly diagnosed cases towards younger age groups, and an adverse distribution of tumour stages in the time of detection. The tumours are most frequently localized in the upper external quadrant. The survival rate is one of the most important parameters for the evaluation of cancer control programs. The Kaplan-Meier method is most frequently used for survival rate analysis in the cancer registries processed in Hakulinen modification. The absolute and relative survival time, particular survival rate with respect to the diagnosis, and age distributed relative survival rate, belong to basic survival parameters. Survival rate analysis requires precise preparation of input data and qualified interpretation of results.
Survival rate data is one of the indirect parameters of the effectiveness of secondary prevention and treatment results for cancer. The survival rate study of female breast cancer in the CR in the time period 1977-1990 was carried out based on the NCR data according to EUROCARE study methodology. The working set of 40, 906 cases was created after data preparation and control. A absolute survival time was calculated by the Kaplan-Meier method, relative survival rate according to Hakulinen. The results show the values of survival rate for the whole set and also values distributed with respect to age, tumour stage, year of diagnosis, and region. The age standardized relative survival rate in the CR for the period 1978-1985 is presented in context with data from the EUROCARE study based on European registries. The interpretation of results cannot be separated from the analysis of health care organisation and system of registration. The same study was carried out for 17 other diagnoses.
Cancer registry data is an important source of long-term collected information for research in descriptive and analytical epidemiology. It used to be exploited for hypothesis statements, further verified by goal-directed analytical studies. The search and analysis of reasons for extremes in occurrence of malignant tumours, or in the results of health care, the study of etiological factors, provision of data for retrospective and prospective studies, and the analysis of carcinogenic factors in cancer treatment are the most frequent field for its applications. The use of registry data must respect the need for individual data protection. Many studies are coordinated at the international level.
The rate of multiple malignancies is steadily increasing. The NCR from Southern Moravia records increasing rate of tumours, recorded as consecutive malignancies the increase from 10.6 % in 1994 to 14.1% in 1997. The average age for detection of primary and secondary tumours is 65.7 and 70.2 respectively. The non-melanoma skin tumours are most frequently detected as primary and secondary tumours for both genders. The next most frequent primary malignancies are colorectal and prostate cancer for men, and breast, corpus uteri and colorectal cancer for women. The most frequent consecutive malignancies are lung, colorectal and prostate cancer for men and breast and colorectal cancer for women. The specifics of the exploited data sources must be respected during the study of multiple malignancies based on the records from medical facilities and from the cancer registry.
Current medical systems increasingly tend to apply a controlled approach towards health care management in oncology as "cancer control programs". These programs include intervention, primary and secondary prevention, and also diagnostics and treatment. They used to be arranged at various levels at the national, regional, district or at medical facility level, etc. Cancer registries are the information backbone for such cancer programs, they allow planning, tracing their course and evaluation of results from the point of view of medicine, their extent and economical needs. The registries can be exploited for goal-directed specification of priorities for these programs and for the evaluation of basic epidemiological parameters and results of health care.
Female breast cancer shows an increase in incidence and mortality in the CR according to the data from NCR, they affect increasingly younger age groups, differences can be also found in regional distribution. The comparison with foreign registry data calls attention towards the unfavourable situation in the field of female breast cancer in the CR. Breast cancer is detected in earlier stages in the countries with developed systems of preventive cancer care, the patients survive longer and long-term mortality trends have a decreasing tendency. While only about 60% of cases are detected in the clinically more favourable stages O, I and II in the CR, these lower stages constitute 80-90% of all cases in foreign countries. The experience from developed countries, where complex "breast cancer programs" (BCP) are introduced, constitutes a strong argument for their introduction in the CR. The BCP, the areal mammographic screening inclusive, should become an integral part of health care. Preliminary steps are presently in progress in the CR, a relevant ministry commission was founded, and a basic expense balance was performed. Foreign experience shows that the introduction of BCP does not lead to an increase in expenses in breast cancer treatment, but rather to their transfer towards prevention.
Data from the cancer registry can also be used for continuous tracking and evaluation of the quality of prevention, diagnostic, treatment and intervention programs. The method of diagnostic verification, extent of disease, detection of early stages and their development trends, survival rate, therapeutic result and economical demands are important parameters for the quality evaluation of these processes.
