1 Cancer Epidemiology Unit and Cancer Registries of Vaud and Neuchâtel, Institut universitaire de médecine sociale et préventive, Lausanne, Switzerland; 2 Cancer Prevention and Control Unit, Institut Català dOncologia, LHospitalet; 3 Department of Public Health, Universitat de Barcelona, Barcelona, Spain; 4 Laboratory of Epidemiology, Istituto di Ricerche Farmacologiche Mario Negri, Milan; 5 Istituto di Statistica Medica e Biometria, Università degli Studi di Milano, Milan, Italy
Received 24 March 2003; revised 30 July 2003; accepted 30 September 2003
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ABSTRACT |
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Key words: Europe, gastric cancer, mortality, time, trends
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Introduction |
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Materials and methods |
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For the present analysis we considered recent trends in mortality from gastric cancer for 25 individual European countries and the Russian Federation. Data for the Russian Federation, and for other Republics included in the former Soviet Union, have been made available in the WHO database from 1980 onwards. Data for Croatia and Slovenia have been made available since 1985, those for the Czech Republic since 1986 and those for Slovakia since 1992. These were subsequently subdivided into the EU, and six central-eastern European countries providing uniform data across the calendar period considered (Bulgaria, Czech Republic, Hungary, Poland, Romania, Slovakia).
In the 1980s, most countries utilized the Ninth Revision of the International Classification of Diseases (ICD-9), but some still used ICD-8, and some adopted the ICD-10 from 1995 onwards. Since differences between various revisions were minor, gastric cancer deaths were re-coded for all countries according to the ICD-9 (code no. 151) [3, 7].
From the matrices of certified deaths and resident populations, age-standardized rates at all ages, at age 3564 years and at age 2044 years were computed on the basis of the world standard population.
The joinpoint regression model was used to describe changes in trends. This type of non-linear regression model has also been called piecewise regression, segmented regression, broken line regression and/or multi-phase regression with the continuity constraint in the literature [6]. In joinpoint analysis, the best fitting points (the joinpoints) are chosen where the rate changes significantly (increase or decrease) [6, 8]. The analysis starts with the minimum number of joinpoint (e.g. zero joinpoints, which is a straight line) and tests whether one or more joinpoints are significant and must be added to the model (up to four joinponts). The tests of significance use a Monte Carlo permutation method. In the final model each joinpoint (if any) informs of a significant change in trend, and an annual percentage change is computed by each of those trends by means of generalized linear models, assuming a Poisson distribution. Significant changes include changes in direction or in the rate of increase or decrease. The annual percentage change is tested to determine whether it is different from the null hypothesis of no change [8]. The joinpoint analyses were performed using the Joinpoint software from the Surveillance Research Program of the US National Cancer Institute (available at http://www-dccps.ims.nci.nih.gov/SRAB).
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Results |
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The main findings from joinpoint regression over the period 19501999 in 20 European countries providing long-term data, the EU, and selected central and eastern European countries are given in Figure 2 and Table 3 for men. Apart from some central (Hungary, Poland) and southern (Spain, Portugal) European countries, whose downward trends started in the 1960s, most countries showed falls in gastric cancer mortality throughout the five decades considered. These were, if anything, larger after the 1960s and 1970s, and showed no evidence of levelling off, in proportional terms. Indeed, in the whole EU, the largest proportional decline (3.83% per year) was observed in the 1990s. As shown in Figure 2, the pattern was similar at age 3564 years.
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Discussion |
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For gastric cancer, death certification has long been sufficiently reliable to permit meaningful inference on trends for most European countries, particularly those from western Europe, as well as for major central and eastern European countries, mostly in population aged <65 years [3]. In any case, it is unlikely that any possible change in diagnostic practices of gastric cancer can explain such widespread and important downward trends as those observed across Europe [10, 11].
The use of joinpoint analysis has allowed an innovative approach to the description of the trends in gastric cancer mortality over the last five decades. Although any modelling technique has inherent problems of interpretation, the key message from joinpoint regression is that, in most of Europe, the fall in gastric cancer mortality is continuing, if anything with a steeper slope, over the most recent calendar period. The estimate of the annual percentage change, however, is a measure of the proportional fall in gastric cancer death rates, and, on a public health level, has to be translated in absolute figures.
During the 1990s, gastric cancer was the main determinant of the fall observed in cancer mortality in the EU [5]. Even assuming, as suggested by the present analysis, a persisting fall in gastric cancer mortality over the next decade, the number of deaths avoided in the first decade of the current century will probably not be greater than 15 000. These figures will remain appreciably larger in central and eastern European countries, and most of all in the Russian Federation, where gastric cancer remains a public health priority [12].
The reasons for the generalized declines in gastric cancer rates throughout Europe are complex and not completely understood. Almost certainly, these include a more varied and affluent diet and better food conservation, including refrigeration, as well as the control of Helicobacter pylori infection [4, 1315] and reduced tobacco smoking, at least in males [16]. Whether improved diagnosis and treatment has also played some role on the favorable trends in gastric cancer throughout Europe, particularly over most recent calendar periods, however, remains open to question [17, 18].
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Acknowledgements |
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FOOTNOTES |
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