title: Increasingly strong reduction in breast cancer mortality due to screening.
abstract: BACKGROUND
  Favourable outcomes of breast cancer screening trials in the 1970s and 1980s resulted in the launch of population-based service screening programmes in many Western countries. We investigated whether improvements in mammography and treatment modalities have had an influence on the effectiveness of breast cancer screening from 1975 to 2008.
  
  
  METHODS
  In Nijmegen, the Netherlands, 55,529 women received an invitation for screening between 1975 and 2008. We designed a case-referent study to evaluate the impact of mammographic screening on breast cancer mortality over time from 1975 to 2008. A total number of 282 breast cancer deaths were identified, and 1410 referents aged 50-69 were sampled from the population invited for screening. We estimated the effectiveness by calculating the odds ratio (OR) indicating the breast cancer death rate for screened vs unscreened women.
  
  
  RESULTS
  The breast cancer death rate in the screened group over the complete period was 35% lower than in the unscreened group (OR=0.65; 95% CI=0.49-0.87). Analysis by calendar year showed an increasing effectiveness from a 28% reduction in breast cancer mortality in the period 1975-1991 (OR=0.72; 95% CI=0.47-1.09) to 65% in the period 1992-2008 (OR=0.35; 95% CI=0.19-0.64).
  
  
  CONCLUSIONS
  Our results show an increasingly strong reduction in breast cancer mortality over time because of mammographic screening.
authors.affiliation: Department of Epidemiology, Biostatistics and HTA, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands. g.vanschoor@ebh.umcn.nl
authors.forename: G
authors.initials: G
authors.lastname: van Schoor
authors.forename: S M
authors.initials: SM
authors.lastname: Moss
authors.forename: J D M
authors.initials: JD
authors.lastname: Otten
authors.forename: R
authors.initials: R
authors.lastname: Donders
authors.forename: E
authors.initials: E
authors.lastname: Paap
authors.forename: G J
authors.initials: GJ
authors.lastname: den Heeten
authors.forename: R
authors.initials: R
authors.lastname: Holland
authors.forename: M J M
authors.initials: MJ
authors.lastname: Broeders
authors.forename: A L M
authors.initials: AL
authors.lastname: Verbeek
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D002277:Carcinoma / Q000175:diagnosis* / Q000401:mortality*; D016022:Case-Control Studies; D015536:Down-Regulation; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods / Q000706:statistics & numerical data; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D015397:Program Evaluation