title: Polyp size and advanced histology in patients undergoing colonoscopy screening: implications for CT colonography.
abstract: OBJECTIVE
  Colorectal cancer screening with diagnostic imaging can detect polyps. The management of patients whose largest polyp is less than 10 mm is uncertain. The primary aim of this study was to determine rates of advanced histology in patients undergoing colorectal cancer screening whose largest polyp is 9 mm or less.
  
  
  METHODS
  Subjects include all asymptomatic adults receiving colonoscopy for screening during 2005 from 17 practice sites, which provide both colonoscopy and pathology reports to the Clinical Outcomes Research Initiative repository. Patients were classified by size of largest polyp. Advanced histology was defined as an adenoma with villous or serrated histology, high-grade dysplasia, or an invasive cancer. Risk factors for advanced histology were determined using Pearson chi(2) and Fisher exact tests.
  
  
  RESULTS
  Among 13,992 asymptomatic patients who had screening colonoscopy, 6360 patients (45%) had polyps, with complete histology available in 5977 (94%) patients. The proportion with advanced histology was 1.7% in the 1- to 5-mm group, 6.6% in the 6- to 9-mm group, 30.6% in the greater than 10-mm group, and 72.1% in the tumor group. Distal location was associated with advanced histology in the 6- to 9-mm group (P = .04) and in the greater than 10-mm group (P = .002).
  
  
  CONCLUSIONS
  One in 15 asymptomatic patients whose largest polyp is 6 to 9 mm will have advanced histology and would undergo surveillance at 3 years based on current guidelines. Because histology is necessary for this decision, most of these patients should be offered colonoscopy. Further study should determine whether patients whose largest polyp is 1-5 mm can be safely followed without polypectomy.
authors.affiliation: Division of Gastroenterology and Hepatology, Oregon Health and Science University, Portland, Oregon 97239, USA. lieberma@ohsu.edu
authors.forename: David
authors.initials: D
authors.lastname: Lieberman
authors.forename: Matthew
authors.initials: M
authors.lastname: Moravec
authors.forename: Jennifer
authors.initials: J
authors.lastname: Holub
authors.forename: Leann
authors.initials: L
authors.lastname: Michaels
authors.forename: Glenn
authors.initials: G
authors.lastname: Eisen
mesh_terms: D000236:Adenoma / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology; D000328:Adult; D000368:Aged; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology; D003111:Colonic Polyps / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000473:pathology; D023881:Colonography, Computed Tomographic; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index