title: Overdiagnosis in the population-based service screening programme with mammography for women aged 40 to 49 years in Sweden.
abstract: OBJECTIVE
  To estimate the level of overdiagnosis of all breast cancers and of invasive breast cancers in women aged 40-49 invited to the subsequent screening rounds in the Swedish service-screening programme 1986-2005.
  
  
  METHODS
  To estimate the level of overdiagnosis in subsequent screening, the rate ratios (RR) of the breast cancer incidence in the study group (women in areas with screening in ages 40-49) and the control group (women in areas with no screening in ages 40-49) were calculated for all breast cancers and for invasive breast cancers. The RR estimates were adjusted for the prescreening difference in incidence between study and control group and for lead time.
  
  
  RESULTS
  The prescreening incidence rate ratio was estimated at 0.92 (95% confidence interval [CI]: 0.88-0.97). The number of breast cancer cases and person-years were 6047 and 3.8 million, and 7790 and 5.2 million, in the study group and control group respectively during the study period. The RR estimate for all cancers was 1.01 (95% CI: 0.94-1.08) when adjusted for prescreening difference and a lead time of 1.2 years. The corresponding estimate for invasive breast cancers was 0.95 (95% CI: 0.88-1.02).
  
  
  CONCLUSIONS
  We found no significant overdiagnosis for women aged 40-49 in the Swedish service screening programme with mammography.
authors.affiliation: Department of Radiation Sciences, Umeå University, 901 87 Umeå, Sweden. barbro.hellquist@oc.umu.se
authors.forename: Barbro Numan
authors.initials: BN
authors.lastname: Hellquist
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Duffy
authors.forename: Lennarth
authors.initials: L
authors.lastname: Nyström
authors.forename: Håkan
authors.initials: H
authors.lastname: Jonsson
mesh_terms: D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D002277:Carcinoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D008403:Mass Screening / Q000379:methods / Q000706:statistics & numerical data*; D008875:Middle Aged; D011153:Population; D013548:Sweden / Q000453:epidemiology