title: Breast cancer risk prediction model: a nomogram based on common mammographic screening findings.
abstract: OBJECTIVE
  To develop a prediction model for breast cancer based on common mammographic findings on screening mammograms aiming to reduce reader variability in assigning BI-RADS.
  
  
  METHODS
  We retrospectively reviewed 352 positive screening mammograms of women participating in the Dutch screening programme (Nijmegen region, 2006-2008). The following mammographic findings were assessed by consensus reading of three expert radiologists: masses and mass density, calcifications, architectural distortion, focal asymmetry and mammographic density, and BI-RADS. Data on age, diagnostic workup and final diagnosis were collected from patient records. Multivariate logistic regression analyses were used to build a breast cancer prediction model, presented as a nomogram.
  
  
  RESULTS
  Breast cancer was diagnosed in 108 cases (31 %). The highest positive predictive value (PPV) was found for spiculated masses (96 %) and the lowest for well-defined masses (10 %). Characteristics included in the nomogram are age, mass, calcifications, architectural distortion and focal asymmetry.
  
  
  CONCLUSIONS
  With our nomogram we developed a tool assisting screening radiologists in determining the chance of malignancy based on mammographic findings. We propose cutoff values for assigning BI-RADS in the Dutch programme based on our nomogram, which will need to be validated in future research. These values can easily be adapted for use in other screening programmes.
  
  
  CONCLUSIONS
  • There is substantial reader variability in assigning BI-RADS in mammographic screening. • There are no strict guidelines linking mammographic findings to BI-RADS categories. • We developed a model (nomogram) predicting the presence of breast cancer. • Our nomogram is based on common findings on positive screening mammograms. • The nomogram aims to assist screening radiologists in assigning BI-RADS categories.
authors.affiliation: National Expert and Training Centre for Breast Cancer Screening, PO Box 6873, 6503 GJ, Nijmegen, The Netherlands. j.timmers@lrcb.nl
authors.forename: J M H
authors.initials: JM
authors.lastname: Timmers
authors.forename: A L M
authors.initials: AL
authors.lastname: Verbeek
authors.forename: J
authors.initials: J
authors.lastname: IntHout
authors.forename: R M
authors.initials: RM
authors.lastname: Pijnappel
authors.forename: M J M
authors.initials: MJ
authors.lastname: Broeders
authors.forename: G J
authors.initials: GJ
authors.lastname: den Heeten
mesh_terms: D000367:Age Factors; D000368:Aged; D000465:Algorithms; D001943:Breast Neoplasms / Q000175:diagnosis*; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods*; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D015999:Multivariate Analysis; D009426:Netherlands; D049451:Nomograms; D015588:Observer Variation; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011336:Probability; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies