Using GIS to Produce Cancer Incidence Maps: A Case Study of Trabzon, Turkey 2. Aim of Study
Study Area The study area is Trabzon where located in the North Eastern part of Turkey and having coast to the Black Sea (Figure 1). The province has 17 towns and 537 villages with 4 664 square km. Its population in 2000 is recorded as 975 137, and according to the data of 2000; the population density of Trabzon is 209. The annual rate of increase in population in 1990- 2000 is nearly 20.3% (DIE, 2002).  Figure 1: The location of Trabzon Province in Turkey Providing Cancer Data and Based Maps Cancer statistics concerning Trabzon province are provided from the Cancer Struggle Department of Health Directorate of Trabzon Province of Turkey. The cancer cases data recorded for the year 2004 was used. During 2004 year, the center has recorded 1939 cancer cases for the Eastern Black Sea Region. Out of these dataset, 1216 cases occurred within the administrative boundaries of Trabzon province were selected for this study. However, as a result of the data quality analysis of these cases, some records of cancer cases lacking adequate address information were excluded. After this elimination, a total of 1150 cancer cases were used in the production of cancer maps. Administrative unit map of Trabzon was used as the base map for the application to cancer cases is demonstrated on it. In this base map, there are graphical information representing the boundaries and the centers of administrative units. The data in the map includes boundaries of counties and villages, and their centers including their populations. The base map was transferred into topological data structure using ArcGIS 9.x software and the data was stored in the shape (.shp) files. This dataset comprises of two data layers, one is administrative boundaries in polygons and the other is administrative centers in points. 4. Creating GIS-based Cancer Density Maps The cancer cases applicable for the study have been determined and the data have been arranged in a database in the Microsoft Office Excel program. Afterwards, the data that form the cancer database have been changed into ‘dbase’ format to be used in the ArcGIS software. ArcGIS software was used in transferring the cancer data into the base map. In this process, the previously arranged graphical data of administrative boundaries of Trabzon province together with district boundaries in the city centre of Trabzon were used as the base graphical data. Each case was marked on the map with a point with the guidance of its address information, generating a new cancer distribution layer (Colak, H.E.,2005). With the production of distribution map of cancer cases for Trabzon province, geographical distributions of cancer cases within Trabzon province for the year 2004 were able to be observed. However, in order to be able to perform some statistical analysis and comparisons, calculation of cancer incidence values for each administrative unit was needed. A cancer incidence rate is the number of new cancers of a specific type occurring in a specified population during a year, usually expressed as the number of cancers per 100,000 populations at risk (URL-3). For this purpose, the number of cases for each administrative unit was determined. With using case numbers and census data of the year 2000, incidence values for each unit was calculated as in the equation below. In this equation the coefficient “k” is 100.000. Incidence rate = (Number of New Cancer Cases / Population) × k [k=100.000] |