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Abstract
Introduction In the past decades, mortality due to breast cancer has declined considerably in Switzerland and other developed countries. The reasons for this decline remain controversial as several factors occurred almost simultaneously, including important advances in treatment approaches, breast cancer awareness and the introduction of mammography screening programmes in many European countries. In Switzerland, mammography screening programmes (MSPs) have existed in some regions for over 20 years but do not yet exist in others. This offers the possibility to analyse its effects with modern spatiotemporal methodology. We aimed to assess the spatiotemporal patterns and the effect of MSPs on breast cancer mortality.
Setting Switzerland.
Participants The study covers breast cancer deaths of the female population of Switzerland during the period 1969–2012. We retrieved data from the Swiss Federal Statistical Office aggregated on a small-area level.
Design We fitted Bayesian hierarchical spatiotemporal models on death rates indirectly standardised by national references. We used linguistic region, degree of urbanisation, duration of population-based screening programmes and socioeconomic index as covariates.
Results In Switzerland, breast cancer mortality in women slightly increased until 1989–1992 and declined strongly thereafter. Until 2009–2012, the standardised mortality ratio declined to 57% (95% CI 54% to 60%) of the 1969–1972 value. None of the other coefficients of the spatial regressions had a significant effect on breast cancer mortality. In 2009–2012, no region had significantly elevated or reduced breast cancer mortality at 95% credible interval level compared with the national mean.
Conclusion There has been a strong reduction of breast cancer mortality from the 1990s onwards. No important spatial disparities were observed. The factors studied (urbanisation, language, duration of population-based MSP and socioeconomic characteristics) did not seem to have an influence on them. Low participation rates and opportunistic screening use may have contributed to the low impact of MSPs.
- neoplasm
- breast cancer
- switzerland
- bayesian disease mapping
- mortality
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Footnotes
Contributors PV, SE conceived of the study. CH carried out the analysis and data acquisition. CH, SE, PV contributed to the analysis of the data and the writing of the manuscript. CH, PV, BT, NPH, CR and SE contributed to interpretation of the findings and critically revised the manuscript. All authors read and approved the final manuscript.
Funding CH was supported by the Cancer League Eastern Switzerland and CH and PV were supported by a grant of the Swiss National Science Foundation with the number 32003B_135769.
Disclaimer The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing interests None declared.
Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data are publically available from the sources stated in the Methods section. Statistical code is available from the corresponding author.