title: Colorectal cancers found after a complete colonoscopy.
abstract: OBJECTIVE
  The incidence of colorectal cancer in patients undergoing colonoscopic surveillance is higher than previously thought. A better understanding of interval cancers is needed to improve surveillance strategies. The objectives of this study were to determine whether interval colorectal cancers were associated with an inadequate earlier colonoscopy, incomplete polypectomy, or aggressive biologic behavior.
  
  
  METHODS
  We searched our institution's cancer registry. Interval cancers were defined as colorectal cancers that developed within 5 years of a complete colonoscopy. These were frequency matched in a 1:2 ratio to patients with sporadic cancers, which were defined as colorectal cancers diagnosed on a patient's first recorded colonoscopy. Patient, colonoscopy, and tumor characteristics of interval and sporadic cancers were compared.
  
  
  RESULTS
  Of the 830 colorectal cancers diagnosed during the study period, 45 patients developed an interval cancer (5.4%; 95% confidence interval, 4.1%-7.2%). Twenty-seven percent of interval cancers developed at previous polypectomy segments, and location of polypectomy segments was predictive of the location of subsequent interval cancers. Interval cancers were 3 times more likely to occur in the right colon and were smaller in size than sporadic cancers. Quality of bowel preparation, individual endoscopist, endoscopist experience, and trainee involvement were not associated with interval cancers. No difference in TNM stage at diagnosis, histologic type or grade, carcinoembryonic antigen level, or 5-year survival was found between interval and sporadic cancers.
  
  
  CONCLUSIONS
  Incomplete polypectomy might play an important role in the development of interval colorectal cancer. No association between other colonoscopy-related factors or tumor characteristics and interval cancers was found.
authors.affiliation: Section of Gastroenterology, Minneapolis VA Medical Center, Minneapolis, Minnesota, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Farrar
authors.forename: Mandeep S
authors.initials: MS
authors.lastname: Sawhney
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Nelson
authors.forename: Frank A
authors.initials: FA
authors.lastname: Lederle
authors.forename: John H
authors.initials: JH
authors.lastname: Bond
mesh_terms: D000368:Aged; D003111:Colonic Polyps / Q000175:diagnosis* / Q000601:surgery; D003113:Colonoscopy / Q000379:methods*; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors