title: Geographic variation in volumetric breast density between screening regions in the Netherlands.
abstract: OBJECTIVE
  Differences in breast density between populations may explain part of the variation in regional breast cancer screening performance. This study aimed to determine whether regional differences in breast density distribution are present in the Dutch screening population.
  
  
  METHODS
  As part of the DENSE trial, mammographic density was measured using a fully-automated volumetric method. The regions in our study were based on the geographic coverage of 14 reading units representing a large part of the Netherlands. General linear models were used.
  
  
  RESULTS
  Four hundred eighty-five thousand and twenty-one screening participants with a median age of 60 years were included (2013-2014). The proportion of women with heterogeneously or extremely dense breasts ranged from 32.5% to 45.7% between regions. Mean percent dense volume varied between 6.51% (95% confidence interval [CI]: 6.46-6.55) and 7.68% (95% CI: 7.66-7.71). Age differences could not explain the variation. Socio-economic status (SES) was positively associated with volumetric density in all analyses (low SES: 6.95% vs. high SES: 7.63%; p trend  < 0.0001), whereas a potential association between urbanisation and breast density only became apparent after SES adjustment.
  
  
  CONCLUSIONS
  There appears to be geographic variation in mammographic density in the Netherlands, emphasizing the importance of including breast density as parameter in the evaluation of screening performance.
  
  
  CONCLUSIONS
  • Mammographic density may affect regional breast cancer screening performance. • Volumetric breast density varies across screening areas. • SES is positively associated with breast density. • Implications of volumetric breast density differences need to be studied further.
authors.affiliation: Radboud Institute for Health Sciences (Department for Health Evidence, Mailbox 133), Radboud university medical center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands. Danielle.vanderWaal@radboudumc.nl.
authors.forename: Daniëlle
authors.initials: D
authors.lastname: van der Waal
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marleen J
authors.initials: MJ
authors.lastname: Emaus
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marije F
authors.initials: MF
authors.lastname: Bakker
authors.affiliation: Dutch Reference Centre for Screening, Nijmegen, The Netherlands.|Department of Radiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: den Heeten
authors.affiliation: Department of Radiology, Radboud university medical center, Nijmegen, The Netherlands.
authors.forename: Nico
authors.initials: N
authors.lastname: Karssemeijer
authors.affiliation: Dutch Reference Centre for Screening, Nijmegen, The Netherlands.|Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Pijnappel
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Wouter B
authors.initials: WB
authors.lastname: Veldhuis
authors.affiliation: Radboud Institute for Health Sciences (Department for Health Evidence, Mailbox 133), Radboud university medical center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
authors.forename: André L M
authors.initials: AL
authors.lastname: Verbeek
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Carla H
authors.initials: CH
authors.lastname: van Gils
authors.affiliation: Radboud Institute for Health Sciences (Department for Health Evidence, Mailbox 133), Radboud university medical center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.|Dutch Reference Centre for Screening, Nijmegen, The Netherlands.
authors.forename: Mireille J M
authors.initials: MJ
authors.lastname: Broeders
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000473:pathology*; D000071060:Breast Density; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology*; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D016014:Linear Models; D042361:Mammary Glands, Human / Q000002:abnormalities / Q000473:pathology; D008327:Mammography / Q000379:methods; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D012111:Residence Characteristics / Q000706:statistics & numerical data
keywords: Breast cancer screening; Digital mammography; Mammographic density; Socio-economic status; Urbanisation