title: Importance of comparison of current and prior mammograms in breast cancer screening.
abstract: OBJECTIVE
  To retrospectively determine the influence of comparing current mammograms with prior mammograms on breast cancer detection in screening and to investigate a protocol in which prior mammograms are viewed only when necessary.
  
  
  METHODS
  Institutional review board approval was not required. Participants gave written informed consent. Twelve experienced screening radiologists read 160 soft-copy screening mammograms twice, once with and once without prior mammograms. Eighty mammograms were obtained in women in whom breast cancer was diagnosed later; the other 80 mammograms had been reported as normal or benign. All cancers were visible in retrospect. Readers located potential abnormalities, estimated likelihood of malignancy for each finding, and indicated whether prior mammograms were considered necessary. The effect of prior mammograms on detection was determined by computing the mean lesion localized fraction in a range of low fractions of nonlesion locations corresponding to operating points in screening. Scores for both reading sessions were combined to assess the effect of making prior mammograms available only when requested. Data were analyzed by comparing the number of localized lesions between the two reading conditions with a paired two-tailed Student t test and applying a linear mixed model to test differences in average mean lesion localized fraction between reading conditions. P values less than .05 indicated statistical significance.
  
  
  RESULTS
  Without prior mammograms, significantly more annotations were made. When only positive cases were considered, no difference was observed. Reading performance was significantly better when prior screening mammograms were available. At fixed lesion localized fraction, nonlesion localized fraction was reduced by 44% (P<.001) on average when prior mammograms were read. Performance was also increased for combined reading mode (ie, when prior mammograms were available on request only). However, this increase was smaller than that when prior mammograms were always available. Prior mammograms were requested in 24%-33% of all cases and were requested more often in positive cases.
  
  
  CONCLUSIONS
  Comparison with prior mammograms significantly improves overall performance and can reduce referrals due to nonlesion locations. Limiting the availability of prior mammograms to cases selected by the reader reduces the beneficial effect of prior mammograms.
authors.affiliation: Department of Radiology, Radboud University Nijmegen Medical Center, Geert Grooteplein 10, 667 Radiology, 6500 HB Nijmegen, the Netherlands. T.Roelofs@rad.umcn.nl
authors.forename: Antonius A J
authors.initials: AA
authors.lastname: Roelofs
authors.forename: Nico
authors.initials: N
authors.lastname: Karssemeijer
authors.forename: Nora
authors.initials: N
authors.lastname: Wedekind
authors.forename: Christian
authors.initials: C
authors.lastname: Beck
authors.forename: Sander
authors.initials: S
authors.lastname: van Woudenberg
authors.forename: Peter R
authors.initials: PR
authors.lastname: Snoeren
authors.forename: Jan H C L
authors.initials: JH
authors.lastname: Hendriks
authors.forename: Marco
authors.initials: M
authors.lastname: Rosselli del Turco
authors.forename: Nils
authors.initials: N
authors.lastname: Bjurstam
authors.forename: Hans
authors.initials: H
authors.lastname: Junkermann
authors.forename: David
authors.initials: D
authors.lastname: Beijerinck
authors.forename: Brigitte
authors.initials: B
authors.lastname: Séradour
authors.forename: Carl J G
authors.initials: CJ
authors.lastname: Evertsz
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D011379:Prognosis; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013382:Subtraction Technique