title: Rate and predictors of early/missed colorectal cancers after colonoscopy in Manitoba: a population-based study.
abstract: OBJECTIVE
  Many of the colorectal cancers (CRCs) diagnosed within 3 years after a colonoscopy are likely because of lesions missed on the initial colonoscopy. In this population-based study, we investigated the rate and predictors of CRCs diagnosed within 3 years of a colonoscopy.
  
  
  METHODS
  We identified individuals 50-80 years of age diagnosed with CRC between 1992 and 2008 from the provincewide Manitoba Cancer Registry. Performance of colonoscopy and history of co-morbidities was determined by linkage to the provincial universal health care insurance provider's physician billing claims and hospital discharges databases. CRCs diagnosed within 6 months of a colonoscopy were categorized as detected CRCs and those 6-36 months after a colonoscopy as early/missed CRCs. Logistic regression analysis was performed to identify the patient, endoscopist, colonoscopy, and CRC factors associated with early/missed CRCs.
  
  
  RESULTS
  Of the 4,883 CRCs included in the study, 388 (7.9%) were early/missed CRCs, with a range of 4.5% of rectum/rectosigmoid cancers in men to 14.4% of transverse colon/splenic flexure cancers in women. Independent risk factors associated with early/missed CRCs included prior colonoscopy, performance of index colonoscopy by family physicians, recent year of CRC diagnosis, and proximal site of CRC.
  
  
  CONCLUSIONS
  This study suggests that approximately 1 in 13 CRCs may be an early/missed CRC, diagnosed after an index colonoscopy in usual clinical practice. Women are more likely to have early/missed CRC. It is unclear if this relates to differences in procedure difficulty, bowel preparation issues, or tumor biology between men and women.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. singh@cc.umanitoba.ca
authors.forename: Harminder
authors.initials: H
authors.lastname: Singh
authors.forename: Zoann
authors.initials: Z
authors.lastname: Nugent
authors.forename: Alain A
authors.initials: AA
authors.lastname: Demers
authors.forename: Charles N
authors.initials: CN
authors.lastname: Bernstein
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D002983:Clinical Competence; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology; D015897:Comorbidity; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008350:Manitoba / Q000453:epidemiology; D008403:Mass Screening; D008875:Middle Aged; D011159:Population Surveillance; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D013997:Time Factors