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Effectiveness of and overdiagnosis from mammography screening in the Netherlands: population based study

BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5224 (Published 05 December 2017) Cite this as: BMJ 2017;359:j5224
  1. Philippe Autier, professor of epidemiology1 2,
  2. Magali Boniol, data scientist2,
  3. Alice Koechlin, statistician1 2,
  4. Cécile Pizot, statistician2,
  5. Mathieu Boniol, professor of biostatistics1 2
  1. 1University of Strathclyde Institute of Global Public Health at iPRI, Allée Claude Debussy, 69130 Ecully, Lyon, France
  2. 2International Prevention Research Institute, Lyon, France
  1. Correspondence to: P Autier philippe.autier{at}i-pri.org
  • Accepted 5 September 2017

Abstract

Objective To analyse stage specific incidence of breast cancer in the Netherlands where women have been invited to biennial mammography screening since 1989 (ages 50-69) and 1997 (ages 70-75), and to assess changes in breast cancer mortality and quantified overdiagnosis.

Design Population based study.

Setting Mammography screening programme, the Netherlands.

Participants Dutch women of all ages, 1989 to 2012.

Main outcome measures Stage specific age adjusted incidence of breast cancer from 1989 to 2012. The extra numbers of in situ and stage 1 breast tumours associated with screening were estimated by comparing rates in women aged 50-74 with those in age groups not invited to screening. Overdiagnosis was estimated after subtraction of the lead time cancers. Breast cancer mortality reductions during 2010-12 and overdiagnosis during 2009-11 were computed without (scenario 1) and with (scenario 2) a cohort effect on mortality secular trends.

Results The incidence of stage 2-4 breast cancers in women aged 50 or more was 168 per 100 000 in 1989 and 166 per 100 000 in 2012. Screening would be associated with a 5% mortality reduction in scenario 1 and with no influence on mortality in scenario 2. In both scenarios, improved treatments would be associated with 28% reductions in mortality. Overdiagnosis has steadily increased over time with the extension of screening to women aged 70-75 and with the introduction of digital mammography. After deduction of clinical lead time cancers, 32% of cancers found in women invited to screening in 2010-12 and 52% of screen detected cancers would be overdiagnosed.

Conclusions The Dutch mammography screening programme seems to have little impact on the burden of advanced breast cancers, which suggests a marginal effect on breast cancer mortality. About half of screen detected breast cancers would represent overdiagnosis.

Footnotes

  • Contributors: PA coordinated the study and wrote the first version of the manuscript. He is the guarantor. AK, CP, MB, and MD did the statistical analyses. All authors have read the final version of the manuscript.

  • Funding: This work was part of internally supported research projects of the International Prevention Research Institute. No external funding was received for this project. The International Prevention Research Institute had no influence on the methods, data analyses, or discussion.

  • Competing interests: All authors have completed the ICMJE form and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not required.

  • Data sharing: Data on breast cancer incidence by stage can be requested from the Integraal Kankercentrum Nederland. Data on breast cancer mortality are available from the WHO mortality database (www.who.int).

  • Transparency: The lead author and manuscript’s guarantor (PA) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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