title: Visually assessed breast density, breast cancer risk and the importance of the craniocaudal view.
abstract: BACKGROUND
  Mammographic density is known to be a strong risk factor for breast cancer. A particularly strong association with risk has been observed when density is measured using interactive threshold software. This, however, is a labour-intensive process for large-scale studies.
  
  
  METHODS
  Our aim was to determine the performance of visually assessed percent breast density as an indicator of breast cancer risk. We compared the effect on risk of density as measured with the mediolateral oblique view only versus that estimated as the average density from the mediolateral oblique view and the craniocaudal view. Density was assessed using a visual analogue scale in 10,048 screening mammograms, including 311 breast cancer cases diagnosed at that screening episode or within the following 6 years.
  
  
  RESULTS
  Where only the mediolateral oblique view was available, there was a modest effect of breast density on risk with an odds ratio for the 76% to 100% density relative to 0% to 25% of 1.51 (95% confidence interval 0.71 to 3.18). When two views were available, there was a considerably stronger association, with the corresponding odds ratio being 6.77 (95% confidence interval 2.75 to 16.67).
  
  
  CONCLUSIONS
  This indicates that a substantial amount of information on risk from percentage breast density is contained in the second view. It also suggests that visually assessed breast density has predictive potential for breast cancer risk comparable to that of density measured using the interactive threshold software when two views are available. This observation needs to be confirmed by studies applying the different measurement methods to the same individuals.
authors.affiliation: Department of Epidemiology, Mathematics and Statistics, Wolfson Institute of Preventive Medicine, Charterhouse Square, London EC1M 6BQ, UK. stephen.duffy@cancer.org.uk
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Duffy
authors.forename: Iris D
authors.initials: ID
authors.lastname: Nagtegaal
authors.forename: Susan M
authors.initials: SM
authors.lastname: Astley
authors.forename: Maureen G C
authors.initials: MG
authors.lastname: Gillan
authors.forename: Magnus A
authors.initials: MA
authors.lastname: McGee
authors.forename: Caroline R M
authors.initials: CR
authors.lastname: Boggis
authors.forename: Mary
authors.initials: M
authors.lastname: Wilson
authors.forename: Ursula M
authors.initials: UM
authors.lastname: Beetles
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Griffiths
authors.forename: Anil K
authors.initials: AK
authors.lastname: Jain
authors.forename: Jill
authors.initials: J
authors.lastname: Johnson
authors.forename: Rita
authors.initials: R
authors.lastname: Roberts
authors.forename: Heather
authors.initials: H
authors.lastname: Deans
authors.forename: Karen A
authors.initials: KA
authors.lastname: Duncan
authors.forename: Geeta
authors.initials: G
authors.lastname: Iyengar
authors.forename: Pam M
authors.initials: PM
authors.lastname: Griffiths
authors.forename: Jane
authors.initials: J
authors.lastname: Warwick
authors.forename: Jack
authors.initials: J
authors.lastname: Cuzick
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Gilbert
mesh_terms: D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008327:Mammography / Q000379:methods*; D008403:Mass Screening / Q000379:methods; D016017:Odds Ratio; D015203:Reproducibility of Results; D012306:Risk; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012984:Software