title: The impact of mammographic screening on breast cancer mortality in Europe: a review of observational studies.
abstract: OBJECTIVE
  To assess the impact of population-based mammographic screening on breast cancer mortality in Europe, considering different methodologies and limitations of the data.
  
  
  METHODS
  We conducted a systematic literature review of European trend studies (n = 17), incidence-based mortality (IBM) studies (n = 20) and case-control (CC) studies (n = 8). Estimates of the reduction in breast cancer mortality for women invited versus not invited and/or for women screened versus not screened were obtained. The results of IBM studies and CC studies were each pooled using a random effects meta-analysis.
  
  
  RESULTS
  Twelve of the 17 trend studies quantified the impact of population-based screening on breast cancer mortality. The estimated breast cancer mortality reductions ranged from 1% to 9% per year in studies reporting an annual percentage change, and from 28% to 36% in those comparing post- and prescreening periods. In the IBM studies, the pooled mortality reduction was 25% (relative risk [RR] 0.75, 95% confidence interval [CI] 0.69-0.81) among invited women and 38% (RR 0.62, 95% CI 0.56-0.69) among those actually screened. The corresponding pooled estimates from the CC studies were 31% (odds ratio [OR] 0.69, 95% CI 0.57-0.83), and 48% (OR 0.52, 95% CI 0.42-0.65) adjusted for self-selection.
  
  
  CONCLUSIONS
  Valid observational designs are those where sufficient longitudinal individual data are available, directly linking a woman's screening history to her cause of death. From such studies, the best 'European' estimate of breast cancer mortality reduction is 25-31% for women invited for screening, and 38-48% for women actually screened. Much of the current controversy on breast cancer screening is due to the use of inappropriate methodological approaches that are unable to capture the true effect of mammographic screening.
authors.affiliation: Department of Epidemiology, Biostatistics and HTA, Radboud University Nijmegen Medical Centre & National Expert and Training Centre for Breast Cancer Screening, Nijmegen, The Netherlands. m.broeders@ebh.umcn.nl
authors.forename: Mireille
authors.initials: M
authors.lastname: Broeders
authors.forename: Sue
authors.initials: S
authors.lastname: Moss
authors.forename: Lennarth
authors.initials: L
authors.lastname: Nyström
authors.forename: Sisse
authors.initials: S
authors.lastname: Njor
authors.forename: Håkan
authors.initials: H
authors.lastname: Jonsson
authors.forename: Ellen
authors.initials: E
authors.lastname: Paap
authors.forename: Nathalie
authors.initials: N
authors.lastname: Massat
authors.forename: Stephen
authors.initials: S
authors.lastname: Duffy
authors.forename: Elsebeth
authors.initials: E
authors.lastname: Lynge
authors.forename: Eugenio
authors.initials: E
authors.lastname: Paci
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D055088:Early Detection of Cancer / Q000009:adverse effects / Q000706:statistics & numerical data; D005060:Europe; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening / Q000009:adverse effects / Q000706:statistics & numerical data