title: Prevalence and risk factors for post-investigation colorectal cancer ("interval cancer") after computed tomographic colonography: protocol for a systematic review.
abstract: Colorectal cancer (CRC) is a common and important disease. There are different tests for diagnosis, one of which is computed tomographic colonography (CTC). No test is perfect, and patients with normal CTC may subsequently develop CRC (either because it was overlooked originally, or because it has developed in the interim). This is termed post-investigation colorectal cancer (PICRC) or "interval cancer". How frequently this occurs after CTC is not known. The purpose of this systematic review and meta-analysis is to use the primary literature to estimate the PICRC rate after CTC, and explore associated factors.
  
  
  
  Primary studies reporting post-investigation colorectal cancer (PICRC) rates after CTC will be identified from PubMed, Embase and Cochrane Register of Controlled Trials databases. Peer-reviewed studies published after 1994 (the year CTC was introduced) will be included and the rate of PICRC within 36 months of CTC recorded. Data will be extracted from selected studies for a random effects meta-analysis. Heterogeneity, risk of bias and publication bias will be assessed, and exploratory analysis will examine factors associated with higher PICRC rates in the literature.
  
  
  
  PICRC rates are the ultimate benchmark of diagnostic quality for colonic investigations. This systematic review and meta-analysis will identify and synthesise evidence to determine PICRC rates after CTC and explore factors that may contribute to higher rates.
  
  
  
  PROSPERO (registration number CRD42016042437 ).
authors.affiliation: Centre for Medical Imaging, University College London, 3rd Floor East, 250 Euston Rd, London, NW, NW1 2PG, UK. andrew.plumb@nhs.net.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Plumb
authors.affiliation: Centre for Medical Imaging, University College London, 3rd Floor East, 250 Euston Rd, London, NW, NW1 2PG, UK.|St. Mark's Academic Institute, St. Mark's Hospital, Harrow, UK.
authors.forename: Anu
authors.initials: A
authors.lastname: Obaro
authors.affiliation: Nuffield Department of Primary Care Health Sciences, Oxford University, Oxford, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fanshawe
authors.affiliation: Centre for Medical Imaging, University College London, 3rd Floor East, 250 Euston Rd, London, NW, NW1 2PG, UK.|Department of Radiology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Ulysses S
authors.initials: US
authors.lastname: Torres
authors.affiliation: St. Mark's Academic Institute, St. Mark's Hospital, Harrow, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Baldwin-Cleland
authors.affiliation: Centre for Medical Imaging, University College London, 3rd Floor East, 250 Euston Rd, London, NW, NW1 2PG, UK.
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.affiliation: St. Mark's Academic Institute, St. Mark's Hospital, Harrow, UK.
authors.forename: David
authors.initials: D
authors.lastname: Burling
mesh_terms: D023881:Colonography, Computed Tomographic; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D006801:Humans; D015995:Prevalence; D012307:Risk Factors; D000078202:Systematic Reviews as Topic
keywords: Colorectal neoplasms; Computed tomographic colonography; Meta-analysis; Protocol; Systematic review