title: Five-year incidence of advanced neoplasia after initial colonoscopy in Japan: a multicenter retrospective cohort study.
abstract: OBJECTIVE
  The National Polyp Study is used as the basis of recommendations for colonoscopic surveillance after polypectomy, establishing an interval of 3 years after removal of newly diagnosed adenomas. The aim of this retrospective cohort study was to estimate the incidence of advanced neoplasia after initial colonoscopy and compare the differences among risk groups.
  
  
  METHODS
  Patients over 40 years who were referred for initial colonoscopy at six institutes were selected. They were classified into four groups based on the initial colonoscopy: A, patients without any adenoma; B, with adenomas of <6 mm only; C, with adenomas of >or=6 mm; D, with any intramucosal cancer. The index lesion (IL) at follow-up colonoscopy was defined as large adenoma >or=10 mm, intramucosal/invasive cancer.
  
  
  RESULTS
  A total of 5309 patients were enrolled in this study. Overall, median follow-up period was 5.1 years. The numbers of eligible patients in the various subgroups were A, 2006; B, 1655; C, 1123; D, 525. A total of 379 ILs were newly diagnosed during follow-up colonoscopy. The cumulative incidence of ILs in each group was A, 2.6%; B, 6.7%; C, 13.4%; and D, 12.6%.
  
  
  CONCLUSIONS
  Patients with any adenomas >6 mm or intramucosal cancer at the initial colonoscopy have a higher risk of advanced neoplasia during follow-up colonoscopy.
authors.affiliation: Endoscopy Division, National Cancer Center Hospital, Tokyo, Japan. tamatsud@ncc.go.jp
authors.forename: Takahisa
authors.initials: T
authors.lastname: Matsuda
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujii
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sano
authors.forename: Shin-ei
authors.initials: SE
authors.lastname: Kudo
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Oda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Igarashi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Iishi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Murakami
authors.forename: Hideki
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Tadakazu
authors.initials: T
authors.lastname: Shimoda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kaneko
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Yoshida
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000453:epidemiology*; D015331:Cohort Studies; D003110:Colonic Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D003113:Colonoscopy; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011159:Population Surveillance; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors