title: Colorectal cancers soon after colonoscopy: a pooled multicohort analysis.
abstract: OBJECTIVE
  Some individuals are diagnosed with colorectal cancer (CRC) despite recent colonoscopy. We examined individuals under colonoscopic surveillance for colonic adenomas to assess possible reasons for diagnosing cancer after a recent colonoscopy with complete removal of any identified polyps.
  
  
  METHODS
  Primary data were pooled from eight large (>800 patients) North American studies in which participants with adenoma(s) had a baseline colonoscopy (with intent to remove all visualised lesions) and were followed with subsequent colonoscopy. We used an algorithm based on the time from previous colonoscopy and the presence, size and histology of adenomas detected at prior exam to assign interval cancers as likely being new, missed, incompletely resected (while previously an adenoma) or due to failed biopsy detection.
  
  
  RESULTS
  9167 participants (mean age 62) were included in the analyses, with a median follow-up of 47.2 months. Invasive cancer was diagnosed in 58 patients (0.6%) during follow-up (1.71 per 1000 person-years follow-up). Most cancers (78%) were early stage (I or II); however, 9 (16%) resulted in death from CRC. We classified 30 cancers (52%) as probable missed lesions, 11 (19%) as possibly related to incomplete resection of an earlier, non-invasive lesion and 14 (24%) as probable new lesions. The cancer diagnosis may have been delayed in three cases (5%) because of failed biopsy detection.
  
  
  CONCLUSIONS
  Despite recent colonoscopy with intent to remove all neoplasia, CRC will occasionally be diagnosed. These cancers primarily seem to represent lesions that were missed or incompletely removed at the prior colonoscopy and might be avoided by increased emphasis on identifying and completely removing all neoplastic lesions at colonoscopy.
authors.affiliation: Department of Veterans Affairs Medical Center, White River Junction, VT and Dartmouth Medical School & The Dartmouth Institute, , Hanover, New Hampshire, USA.
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Robertson
authors.forename: David A
authors.initials: DA
authors.lastname: Lieberman
authors.forename: Sidney J
authors.initials: SJ
authors.lastname: Winawer
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Ahnen
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: Arthur
authors.initials: A
authors.lastname: Schatzkin
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Cross
authors.forename: Ann G
authors.initials: AG
authors.lastname: Zauber
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: Peter
authors.initials: P
authors.lastname: Lance
authors.forename: E Robert
authors.initials: ER
authors.lastname: Greenberg
authors.forename: María Elena
authors.initials: ME
authors.lastname: Martínez
mesh_terms: D000236:Adenoma / Q000473:pathology* / Q000601:surgery; D000367:Age Factors; D000368:Aged; D000465:Algorithms; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology* / Q000601:surgery; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D013997:Time Factors; D014481:United States / Q000453:epidemiology
keywords: Adenoma; Colonoscopy; Colorectal cancer