title: Screen detection of ductal carcinoma in situ and subsequent incidence of invasive interval breast cancers: a retrospective population-based study.
abstract: BACKGROUND
  The value of screen detection and treatment of ductal carcinoma in situ (DCIS) is a matter of controversy. At present, the extent to which the diagnosis and treatment of DCIS could prevent the occurrence of invasive breast cancer in the future is not clear. We sought to estimate the association between detection of DCIS at screening and invasive interval cancers subsequent to the relevant screen.
  
  
  METHODS
  We obtained aggregate data for screen-detected cancers from 84 local screening units within 11 regional Quality Assurance Reference Centres in England, Wales, and Northern Ireland from the National Health Service Breast Screening Programme. Data for DCIS diagnoses were obtained for women aged 50-64 years who were invited to and attended mammographic breast screening from April 1, 2003, to March 31, 2007 (4 screening years). Patient-level data for interval cancer arising in the 36 months after each of these were analysed by Poisson regression with invasive interval cancer screen detection rate as the outcome variable; DCIS detection frequencies were fitted first as a continuous and then as a categorical variable. We repeated this analysis after adjustment with both small size and high-grade invasive screen-detected cancers.
  
  
  RESULTS
  We analysed data for 5,243,658 women and on interval cancers occurring in the 36 months after the relevant screen. The average frequency of DCIS detected at screening was 1·60 per 1000 women screened (median 1·50 [unit range 0·54-3·56] [corrected to] per 1000 women). There was a significant negative association of screen-detected DCIS cases with the rate of invasive interval cancers (Poisson regression coefficient -0·084 [95% CI -0·13 to -0·03]; p=0·002). 90% of units had a DCIS detection frequency within the range of 1·00 to 2·22 per 1000 women; in these units, for every three screen-detected cases of DCIS, there was one fewer invasive interval cancer in the next 3 years. This association remained after adjustment for numbers of small screen-detected invasive cancers and for numbers of grade 3 invasive screen-detected cancers.
  
  
  CONCLUSIONS
  The association between screen-detected DCIS and subsequent invasive interval cancers suggests that detection and treatment of DCIS is worthwhile in prevention of future invasive disease.
  
  
  BACKGROUND
  UK Department of Health Policy Research Programme and NHS Cancer Screening Programmes.
authors.affiliation: Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, UK. Electronic address: s.w.duffy@qmul.ac.uk.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Duffy
authors.affiliation: Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, UK.
authors.forename: Amanda
authors.initials: A
authors.lastname: Dibden
authors.affiliation: Centre for Cancer Prevention, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, UK.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Michalopoulos
authors.affiliation: Centre for Cancer Prevention, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, UK.
authors.forename: Judith
authors.initials: J
authors.lastname: Offman
authors.affiliation: Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Queen Mary University of London, Wolfson Institute of Preventive Medicine, London, UK.
authors.forename: Dharmishta
authors.initials: D
authors.lastname: Parmar
authors.affiliation: East Midlands QARC, Nottingham University Hospital City Campus, Nottingham, UK.
authors.forename: Jacquie
authors.initials: J
authors.lastname: Jenkins
authors.affiliation: East of England QARC, Histon, Cambridge, UK.
authors.forename: Beverley
authors.initials: B
authors.lastname: Collins
authors.affiliation: London QARC, London, UK.
authors.forename: Tony
authors.initials: T
authors.lastname: Robson
authors.affiliation: Yorkshire and Humber QARC, Newcastle upon Tyne, UK.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Scorfield
authors.affiliation: North West QARC, Albert St, Hollinwood, Oldham, UK.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Green
authors.affiliation: Northern Ireland QARC, Belfast, UK.
authors.forename: Clare
authors.initials: C
authors.lastname: Hall
authors.affiliation: South Central QARC, Oxford, UK.
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Liao
authors.affiliation: South East Coast QARC, Battle, East Sussex, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Ryan
authors.affiliation: South West QARC, Clifton, Bristol, UK.
authors.forename: Fiona
authors.initials: F
authors.lastname: Johnson
authors.affiliation: Public Health Wales, Cardiff, UK.
authors.forename: Guy
authors.initials: G
authors.lastname: Stevens
authors.affiliation: West Midlands QARC, Public Health Building, University of Birmingham, Birmingham, UK.
authors.forename: Olive
authors.initials: O
authors.lastname: Kearins
authors.affiliation: National Cancer Screening Programmes, Sheffield, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Sellars
authors.affiliation: National Cancer Screening Programmes, Sheffield, UK.
authors.forename: Julietta
authors.initials: J
authors.lastname: Patnick
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology