title: Is the three year breast screening interval too long? Occurrence of interval cancers in NHS breast screening programme's north western region.
abstract: OBJECTIVE
  To report the detection rate of interval cancers in women screened by the NHS breast screening programme.
  
  
  METHODS
  Detection of interval cancers by computer linkage of records held by the screening centres in the North Western Regional Health Authority with breast cancer registrations at the regional cancer registry.
  
  
  METHODS
  North Western Regional Health Authority.
  
  
  METHODS
  137,421 women screened between 1 March 1988 and 31 March 1992 who had a negative screening result.
  
  
  RESULTS
  297 invasive interval cancers were detected. The rate of detection of interval cancers expressed as a proportion of the underlying incidence was 31% in the first 12 months after screening, 52% between 12 and 24 months, and 82% between 24 and 36 months.
  
  
  CONCLUSIONS
  The incidence of interval cancers in the third year after breast screening approaches that which would have been expected in the absence of screening and suggests that the three year interval between screens is too long.
authors.affiliation: Centre for Cancer Epidemiology, Christie Hospital NHS Trust, Withington, Manchester.
authors.forename: C B
authors.initials: CB
authors.lastname: Woodman
authors.forename: A G
authors.initials: AG
authors.lastname: Threlfall
authors.forename: C R
authors.initials: CR
authors.lastname: Boggis
authors.forename: P
authors.initials: P
authors.lastname: Prior
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography; D008403:Mass Screening / Q000458:organization & administration*; D008498:Medical Record Linkage; D008875:Middle Aged; D013222:State Medicine / Q000458:organization & administration; D013997:Time Factors; D006113:United Kingdom