Country and Registry characteristics
Greece
Greece is a European Union member state situated in the Balkan peninsula of South-Eastern Europe on a territory of 131,990 km2. The population (11 million people) is predominantly urban (72.8%) and is concentrated mainly in the administrative centers of its51 districts. The Nationwide Registry for Childhood Hematological Malignancies (NARECHEM) in Greece is a specialized hospital based Registry operating since 1996, including all newly diagnosed cases in an average of 1.7 million children - less than 15 years of age- per year in the six pediatric hematology-oncology units of the country [1]. NARECHEM is managed by the Department of Hygiene, Epidemiology and Medical Statistics of the National and Kapodistrian University of Athens Medical School, functions under internationally approved quality control protocols and contributes data from Greece to the ACCIS/IICC-3, EUROCARE and EUROCIM studies under the instructions of the International Agency for Research on Cancer (IARC). The completeness of the registration process reaches nearly 100%.
Specifically, demographic data are collected in each Unit through interviews with the children’s guardians conducted by specially trained health professionals, whereas the treating physicians provide clinical and active follow up survival data. Data on the urbanization of the place of residence at diagnosis of the index child are derived according to the postal codes reported by the guardian.
During the 15-year study period (1996-2010) for which data were available, a total of 1637 children (1215 cases with leukemia and 422 cases with lymphoma) were retrieved from the Registry. Data on the underlying childhood population for the calculation of incidence and mortality data by year, age, and gender were provided by the Hellenic Statistical Authority. The Authority also contributed formally collected, through death registration, mortality data [2].
Bulgaria
Bulgaria is situated in South-Eastern Europe on a territory of 110,993 km2. The population of 7,5 million people is predominantly urban and is concentrated mainly in the administrative centers of its28 districts; children 0-14 years old represent 13.7% of the Bulgarian population (as of 31.12.2010). The Mandatory health insurance system was introduced in the year 2000; it is designed as a state monopoly and it is socially oriented. The Minister of Health defines the Guaranteed Medical Services Package and supervises its observance. Cancer care is provided in the National Hospital of Oncology (NHO), Regional Oncology Centers (ROC), University and some Municipality hospitals, where facilities for complex treatment are available. Childhood cancer cases are treated in the Pediatric Departments of the University hospitals; there are also three main centers especially for the treatment of hematological malignancies in children. Compulsory registration of malignant neoplasms is regulated by the Ministry of Health Instruction (1964) and Orders (1990, 2011). Cancer registration is funded by the Ministry of Health.
The Bulgarian National Cancer Registry (BNCR) was established in 1952. It covers the whole territory of Bulgaria and collects information about cancer cases for all age groups. The estimated completeness of registration is about 95%. ICD10 topography and morphology codes are used. All cancer patients are followed-up until their death or loss of contact. Information about death dates and reasons is received four times a year from the National system for civil registration (ESGRAON). Number of cancer deaths and population figures for each year and 5-year age groups by sex are received from the National Statistical Institute [3].
The data about incident cases (675 leukemias and 292 lymphomas) and deaths for the period 1996-2009 were used in this study. The population number and structures at the end of each year were calculated on the basis of the population data for the preceding year and the data for natural and mechanical movement of the population during the current year.
Moscow
Russian Federation is the country in the northern Eurasia situated on a territory of 17,075,400 km2. With 143,000,000 population Russia is the ninth most populous nation. 73% of the population lives in urban areas while 27% in rural ones. Medical care is free for all citizens and guaranteed the Russian Constitution. Cancer care is provided in federal cancer centers, regional oncological hospitals and in some municipal hospitals. Childhood population < 15 years (21,401,000) represents 15.1% of the whole population. The nationwide cancer registration was established in the former USSR in 1953. However, this registration system does not take into account current international recommendations on stratification and data analysis of childhood cancer cases. To overcome these limitations the first comprehensive childhood population-based Cancer Registry was set up in Moscow Region (MR) in 2000 by the Ministry of Healthcare and Social Development of Moscow Region and Federal Research Center of Pediatric Hematology, Oncology and Immunology (Moscow). Moscow Region (Oblast) is a federal subject of Russian Federation and located in the Eastern part of Russia and is the second most populous federal subject with pediatric population (0-14 years) being 893,601 children in 2010. Moscow city is not an administrative part of the region. The only department which provides healthcare for children and adolescents with cancer within Moscow Region is located in Moscow Regional Oncological Hospital. Up to 50% of patients undergo anticancer treatment in the federal cancer centers in Moscow city which is the independent administrative territory.
The data are collected using both active search and passive retrieval. Multiple sources of information are used, including discharge letters from cancer hospitals, data from pathology laboratories and from the General Cancer Registry of Moscow Region. According to the national law oncologists are obliged to fill a special notification form on newly diagnosed children with cancer. The Childhood Cancer Registry has access to the database of Ministry of Healthcare of Moscow Region, which contains information on patients referred to federal cancer centers. In addition, the Registry has established close collaboration with primary care pediatricians. Apart from the special notification form on newly diagnosed patients, an additional form on patients who have finished anticancer therapy form has been created. By the regional law this form is the document of the obligatory annual medical reporting of pediatricians of municipal districts. Follow-up information is collected by active search in hospital databases and by passive retrieval of notification forms filled by primary care pediatricians. Indefinable death certificates are not available to the Registry; nevertheless, the Registry has access to the depersonalized cancer mortality database of Moscow Region and special requests are sent to primary care pediatricians to trace back other records for these patients. The completeness of registration is estimated to be higher than 90%.
Annual population estimates in Moscow Region were based on the data of the population census in Russian Federation in 2002 and were received from Moscow Regional Committee of Federal State Statistics Service. The dataset for 2000-2010 was used for this study (403 leukemias and 158 lymphomas).
Antalya and Izmir, Turkey
Turkey occupies 779,452 km2 at the crossroads between Europe, Asia and the Middle East, with a population of 73.6 millions.
Antalya is situated in the southern part of Turkey, in the Mediterranean region. The population of Antalya is approximately 2 million and 70% of the inhabitants live in urban areas. The Antalya population-based Cancer Registry was established in 1994. The Registry collects information for all cancer cases arising in Antalya according to the international standards; follow-up in the Antalya Registry is active. The completeness of the registration is approximately 95.4%.The dataset spanning 1998-2008 was used for this study (323 leukemias and 121 lymphomas). Annual population estimates were based on the provincial annual primary health care population records before 2008 and the annual population estimates of Turkish Statistical Institute since 2008.
Izmir is a province in the western extremity of Anatolia, at the western part of the country and it is surrounded by the Aegean sea enclosing the Gulf of İzmir. Its area is 11,973 km2 and is one of Turkey’s most densely populated areas with 3.96 million inhabitants, out of which 70.2% live in urban areas. Izmir has a typical Mediterranean climate which is characterized by long, hot and dry summers; and mild to cool, rainy winters.
Izmir Cancer Registry (ICR) is a provincial population based Registry established in 1993 as a starting point and eventually has become the core of the Cancer Registry system of Turkey stepwise. ICR collects information for all cancer cases arising in its catchment area and follows the international standards for cancer registration during all processes. The completeness of the registration is higher than 95%. Follow-up information is collected actively by using several different methods, including matching the cases with death certificates, active search in hospital databases, telephone calls to the patients’ parents or receiving information from the patients’ family physicians. The dataset for 1996-2007 was used for this study (425 leukemias and 190 lymphomas). Annual population estimates were based on the provincial annual primary health care population records before 2008 and the annual population estimates of Turkish Statistical Institute since 2008. ICD-O-3 coding and IACR/ENCR rules for multiple primary are used in Izmir and Antalya.
Data analysis: incidence and mortality rates by country
Incidence data were ICD-O-3 coded or recoded, whereas mortality data were ICD-9 coded and are presented by major childhood hematological malignancy, namely leukemias and lymphomas during the comparable periods available in each Registry. In order to smooth any artefactual variations due to possible excessive random fluctuations, average crude (IR) and age adjusted (AIR) incidence rates on the WHO standard population per 1,000,000, as well as crude (MR) and age-adjusted (AMR) mortality rates per 1,000,000 were calculated for each country in two time periods i.e., for the average of the first three and the average of the last three available years in each country. The age-adjusted rates of each time period were compared among the five Registries using the direct method and the ratio between the two corresponding rates [4]. The Bonferroni correction was used for the evaluation of p-values in light of multiple comparisons; the threshold for comparisons regarding incidence was 0.05/20=0.0025 (10 comparisons for the first three and 10 comparisons for the last three years), whereas regarding mortality the threshold was 0.05/6=0.0083 (three comparisons for the first three and three comparisons for the last three years).
Incidence and mortality time trends by country
Childhood leukemia and lymphoma incidence and mortality time trends during the specified study period in each of the five Registries were calculated using Poisson modeling of the number of new cases or deaths, rather than focusing on rates. This analysis accommodates the fact that rates may rely on very different underlying population structures and that some figures are relatively small, but it is less straightforward [5].
References
1. Nationwide Registry of Childhood Hematological Malignancies. NARECHEM Official Site.
2. Hellenic Statistical Authority. Statistical Database.
3. National Statistical Institute of Bulgaria. Statistical Database.
4. Jensen OM, Parkin DM, MacLennan CS, Muir CS, Skeet RG. (1991) Cancer Registration: Principles and Methods. IARC Scientific Publication No. 95. Lyon, France: International Agency for Research on Cancer.
5. Philippakis A, Hemenway D, Alexe DM, Dessypris N, Spyridopoulos T, Petridou E (2004) A quantification of preventable unintentional childhood injury mortality in the United States. Inj Prev 10: 79-82.