Estonia
Mati Rahu
Estonia is bound to the west and north by the Baltic Sea, to the east by the Russian Federation and to the south by Latvia. The country lies between 57o30' and 59o49' N, and 21o45' and 28o15' E. The total area of Estonia is 45,215 km2, the maximum distance from north to south is 255, and from west to east 360 km. The highest point is 318 m. Estonia has over 1500 islands, the largest being Saaremaa (2 673 km2) and Hiiumaa (970 km2). The mean annual temperature ranges from 6.0°C in the west to 4.2°C in the east. The mean annual precipitation ranges from under 500 mm on the coast to almost 700 mm in the highlands. In general, the climate is similar to central Sweden or southern Finland. Estonia is rich in inland water bodies, with over 1400 natural and man-made lakes. Forests consisting mostly of coniferous trees cover over 40% of the country. The capital, Tallinn, is located on the north coast of Estonia, about 80 km south of Helsinki. The population at the time of the 1989 census was 1.6 million (731 392 males and 834 270 females). Estonia is divided into 15 counties. The five largest towns are Tallinn (479,000 inhabitants), Tartu (113,000), Narva (81,000), Kohtla-Järve (77,000) and Pärnu (52,000). 28.5% of the population lives in rural areas. The major nationalities are Estonians (61.5%), Russians (30.3%) and Ukrainians (3.1%). About 26% of the population were foreign-born. In 1989, 43% of the working population were employed in industry and trade, 17% in the health services, physical recreation, social security, education, science, culture and the arts, 13% in agriculture, 10% in transport and communications, and 9% in public catering, state purchasing, supply and sales. Life expectancy at birth in 19861991 was 65.7 years for males and 75.0 for females. In 1990, the ratio of live births to legal abortions was 1:1.3. The birth rate was 14.1 and the death rate 12.3 per thousand. The infant mortality rate was 12.4 per thousand live births. The leading causes of death were cardiovascular diseases (61%), tumours (16%) and injury and poisoning (11%). The number of divorces per thousand marriages was 491.
Cancer registration
Cancer registration in Estonia dates back to 1953, when compulsory registration of incident cases of cancer was introduced in the former USSR. During 1953-1967 short and incomplete annual reports were produced. Since 1961, cases detected on the basis of a death certificate have been added to the database [1]. In 1968-1970 cancer registration became centralised in Estonia, and thus, core documentation and satisfactory incidence data are available since 1968. During the period 1971-1975 an attempt was made to use a computer for registration, but unsuccessfully, mainly due to inadequate software. In 1976 a new stage in registration began, and by order of the Ministry of Health on January 16, 1978, the Estonian Cancer Registry (ECR; Eesti Vähiregister) was founded. Up to the end of 1991 the ECR consisted of two informal subdivisions. One of them Department of Cancer Statistics belonged to the Estonian Cancer Centre (former Tallinn Cancer Dispensary), and its task was data collection. Another subdivision now the Department of Epidemiology and Biostatistics located in the Institute of Experimental and Clinical Medicine (IECM) was responsible for statistical and epidemiological analysis and interpretation of the data. Each year both of these parts of the registry made a business contract with the former Public Health Information and Data Processing Centre that owned computers and staff for data processing. In December 1991, the Department of Cancer Statistics was renamed the Estonian Cancer Registry. In 19911993 the ECR was on the verge of vanishing. In 1994 major reorganisations in the ECR took place, and the routine activities of the registry were renewed. The Department of Epidemiology and Biostatistics, IECM continues cancer registration data analysis and research based on these data. In Estonia, every health-care institution where cancer was diagnosed is obliged to send a notification form to the ECR. Data recorded includes name, sex, date of birth, place of birth, nationality, marital status, usual residence, date of diagnosis, site of tumour, histological diagnosis, clinical stage, basis of diagnosis and the first course of treatment. The names of the notifying health-care institution and of the notifying physician are also recorded. The anatomical site of tumours is coded according to the ICD-9, and the histological type is coded according to the ICD-O (First Edition). After coding, the data is entered into the database through an on-line data entry system. Each patient is assigned a unique registration number. At the time of entry a limited amount of editing is performed. Additional intra- and interfield edits are done after input. Computer files are updated as new information is received and checked. If the information received is incomplete, the ECR makes an inquiry to the health-care institution or population registry. Completeness of cancer registration is thought to be 95-98%. There are no special studies concerning the completeness and accuracy of cancer registration data. Performing of audits to verify that registration standards have been followed is hampered because data reporting, coding, analysis and management rules are only marginally documented. During recent years the IARC and IACR rules for multiple primaries have been followed, but there is no consistency over the whole period of cancer registration in Estonia. A patient is followed-up until death/emigration. At annual intervals, all death certificates kept in the Estonian State Department of Statistics (at the moment the Statistical Office of Estonia) are linked with the database of the ECR. There are no 'death certificate only cases'. If a death certificate is the first notification of a cancer case, the certifying physician/hospital is contacted to obtain additional information. If the evidence for cancer is sufficiently strong, the case is entered into the computer.In 1988-1992, microscopical (histological/cytological/ hematological) confirmation of diagnosis for all sites was 81% in males and 85% in females [2]. For the Atlas, mortality data were derived from the ECR's files in order to calculate mortality rates comparable to incidence rates, but not to generate a competitive set of mortality data. Actually, mortality statistics are the responsibility of the Statistical Office of Estonia, but due to limitations in manual processing and in tabulated site coverage in an earlier period [3], that data are not used in the Atlas.Estimates of the population of Estonia were derived from the files in the corresponding monograph [4]. For the purposes of this project, initial data on cancer incidence and mortality has been presented for the five largest towns and 15 counties. When taking into consideration incident cases, lung, stomach and prostate were the most frequent cancer sites in males. In females, breast cancer ranked first, followed by skin (including basaliomas) and stomach cancers. Lung, stomach and prostate were the leading sites among cancers that caused death of male patients. In females, breast, stomach and ovary were the most frequent sites among cancer deaths [4]. From 1968-1992, the overall cancer incidence (age standardised rates) increased 24% for males and 12% for females. Over this period, cancer mortality increased 18% for males, and it was stable for females. The most substantial increase in incidence and mortality took place for oral cancer and skin melanoma. A decrease was most pronounced for stomach and cervical cancers [4]. Up to 1991, annual incidence, mortality, prevalence and treatment data were routinely provided as a part of the Soviet Union public health statistics system. These obligatory annual statistical reports had to be completed some weeks after the end of each calendar year, and their quality is questionable [3]. Other, more informative and reliable tabulations mainly concerning absolute numbers, crude, age-specific and age-standardized rates, calculated and analysed at the Department of Epidemiology and Biostatistics, have been used for the purposes of descriptive epidemiology. A statistical compendium 'Cancer in Estonia 1968-1992: Incidence, Mortality, Prevalence, Survival' was published in 1996 [2]. Some analytical epidemiological studies have also been based on the data of the ECR.
References
1. Rahu M. Cancer epidemiology in the former Soviet Union. Epidemiology 1992;3:46470.
2. Thomson H, Rahu M, Aareleid T, Gornoi K. Cancer in Estonia 1968-1992: Incidence, mortality, prevalence, survival. Institute of Experimental and Clinical Medicine, Tallinn 1996.
3. Leinsalu M, Rahu, M. Time trends in cancer mortality in Estonia, 1965-1989. Int J Cancer 1993;53:9148.
4. EIPRC, IECM. Rahvastiku soovanuskoostis: maakonnad 1979-1989 Population age structure: Counties 1979-1989. RU Seeria C No. 2. Estonian Interuniversity Population Research Centre, and Institute of Experimental and Clinical Medicine, Tallinn 1994.