title: Trends in breast cancer mortality in Sweden before and after implementation of mammography screening.
abstract: BACKGROUND
  Incidence-based mortality modelling comparing the risk of breast cancer death in screened and unscreened women in nine Swedish counties has suggested a 39% risk reduction in women 40 to 69 years old after introduction of mammography screening in the 1980s and 1990s.
  
  
  OBJECTIVE
  We evaluated changes in breast cancer mortality in the same nine Swedish counties using a model approach based on official Swedish breast cancer mortality statistics, robust to effects of over-diagnosis and treatment changes. Using mortality data from the NordCan database from 1974 until 2003, we estimated the change in breast cancer mortality before and after introduction of mammography screening in at least the 13 years that followed screening start.
  
  
  RESULTS
  Breast mortality decreased by 16% (95% CI: 9 to 22%) in women 40 to 69, and by 11% (95% CI: 2 to 20%) in women 40 to 79 years of age.
  
  
  CONCLUSIONS
  Without individual data it is impossible to completely separate the effects of improved treatment and health service organisation from that of screening, which would bias our results in favour of screening. There will also be some contamination of post-screening mortality from breast cancer diagnosed prior to screening, beyond our attempts to adjust for delayed benefit. This would bias against screening. However, our estimates from publicly available data suggest considerably lower benefits than estimates based on comparison of screened versus non-screened women.
authors.affiliation: Faculty of Medicine, Department of Public Health, University of Helsinki, Helsinki, Finland. jari.haukka@helsinki.fi
authors.forename: Jari
authors.initials: J
authors.lastname: Haukka
authors.forename: Graham
authors.initials: G
authors.lastname: Byrnes
authors.forename: Mathieu
authors.initials: M
authors.lastname: Boniol
authors.forename: Philippe
authors.initials: P
authors.lastname: Autier
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D016208:Databases, Factual / Q000706:statistics & numerical data; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography / Q000379:methods*; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009026:Mortality / Q000639:trends; D015203:Reproducibility of Results; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors