title: Post-colonoscopy colorectal cancer (PCCRC) rates vary considerably depending on the method used to calculate them: a retrospective observational population-based study of PCCRC in the English National Health Service.
abstract: OBJECTIVE
  Post-colonoscopy colorectal cancer (PCCRC) is a key quality indicator of colonoscopy. This study compares methods for defining PCCRC rates, proposes a new method of calculating them and quantifies them across the English National Health Service (NHS).
  
  
  METHODS
  This retrospective observational population-based study involved all individuals with a first primary diagnosis of colorectal cancer made between 2001 and 2010 and treated in the English NHS. Previously published methods for deriving PCCRC rates were applied to the linked routine health data for this population to investigate the effect on the rate. A new method, based on the year of the colonoscopy rather than colorectal cancer diagnosis, was then used to calculate PCCRC rates.
  
  
  RESULTS
  Of 297,956 individuals diagnosed with colorectal cancer, a total of 94,648 underwent a colonoscopy in the 3 years prior to their diagnosis. The application of the published methods and exclusion criteria to the dataset produced significantly different PCCRC rates from 2.5% to 7.7%. The new method demonstrates that PCCRC rates within 3 years of colonoscopy (without exclusions) decreased in the English NHS over 8 years, falling from 10.6% to 7.3% for colonoscopies performed in 2001 and 2007 respectively.
  
  
  CONCLUSIONS
  The method used to determine PCCRC rates significantly affects findings with potential to substantially underestimate rates. To enable international benchmarking there needs to be a standardised method for defining PCCRC. This study proposes a new methodology using colonoscopy as a denominator and between 2001 and 2007 this method indicated an 8.6% PCCRC rate across the English NHS. It also demonstrated PCCRC rates have fallen over time.
authors.affiliation: Cancer Epidemiology Group, Leeds Institute of Cancer & Pathology, University of Leeds, St James's Institute of Oncology, St James's University Hospital, Leeds, UK.
authors.forename: Eva J A
authors.identifier: http://orcid.org/0000-0002-1075-6544
authors.initials: EJ
authors.lastname: Morris
authors.affiliation: University Hospital of North Tees, Hardwick, Stockton on Tees, UK Colorectal Site Specific Clinical Reference Group, National Cancer Intelligence Network, London, UK University of Durham, Durham, UK.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Rutter
authors.affiliation: Colorectal Site Specific Clinical Reference Group, National Cancer Intelligence Network, London, UK John Goligher Colorectal Unit, St James's Institute of Oncology, St James's University Hospital, Leeds, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Finan
authors.affiliation: National Cancer Registration Service, Northern and Yorkshire Office, St James's Institute of Oncology, St James's University Hospital, Leeds, UK.
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
authors.affiliation: Gloucestershire Hospitals NHS Foundation Trust, Gloucester, UK.
authors.forename: Roland
authors.initials: R
authors.lastname: Valori
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009313:National Health Programs / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D013997:Time Factors
keywords: COLONOSCOPY; COLORECTAL CANCER