title: Overdiagnosis in breast cancer: design and methods of estimation in observational studies.
abstract: OBJECTIVE
  In recent years observational epidemiological studies have been used to estimate overdiagnosis in breast cancer screening. These estimates vary widely. In this paper we present some of the methodological issues which explain the large variability of the reported findings.
  
  
  METHODS
  Different types of observational studies were identified according to study design, definition of the population, adjustment for breast cancer risk and adjustment for lead time.
  
  
  RESULTS
  The majority of observational studies that have estimated breast cancer overdiagnosis have analyzed temporal trends or geographical differences in breast cancer incidence. Estimates of overdiagnosis in a dynamic population vary widely, from 4% to 52%. Only a few studies have used the cohort approach and they found estimates varying from 1% to 5%.
  
  
  CONCLUSIONS
  The cohort approach is preferable to the analysis of a dynamic population because it allows the follow-up of a group of women who have had the opportunity for screening and evaluates if there is sufficient follow-up after the last screen.
authors.affiliation: Clinical and Descriptive Epidemiology Unit, ISPO, Florence, Italy.
authors.forename: Donella
authors.initials: D
authors.lastname: Puliti
authors.forename: Guido
authors.initials: G
authors.lastname: Miccinesi
authors.forename: Eugenio
authors.initials: E
authors.lastname: Paci
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology; D003951:Diagnostic Errors; D055088:Early Detection of Cancer / Q000295:instrumentation / Q000379:methods*; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D015994:Incidence; D012107:Research Design; D018570:Risk Assessment; D040242:Risk Reduction Behavior; D014481:United States / Q000453:epidemiology; D016387:Women's Health