title: Risk factors for colorectal cancer in Crohn's colitis: a case-control study.
abstract: BACKGROUND
  Few data exist regarding exposures associated with colorectal cancer (CRC) in patients with Crohn's colitis. The aim of this study was to identify exposures that alter the risk of CRC in patients with Crohn's colitis.
  
  
  METHODS
  The Research Patient Database Registry at Massachusetts General Hospital was searched to identify cases and controls. Cases had a confirmed diagnosis of Crohn's disease involving at least one third of the colon and a confirmed diagnosis of colorectal adenocarcinoma. Matched controls were randomly chosen from the same source population. Paired univariate analysis was performed to develop an odds ratio (OR) for each exposure.
  
  
  RESULTS
  Twenty-seven patients were found to have Crohn's colitis and CRC. Colonoscopy performed for screening or surveillance was associated with an OR of 0.21 (95% CI 0.04-0.77; P=0.02). Nonsignificant trends for a protective effect included prior appendectomy (OR 0.30; 95% CI 0.05-1.17; P=0.10) and regular 5-aminosalicylate use (OR 0.30; 95% CI 0.05-1.17; P=0.10). Smoking history was associated with a 4-fold-increased risk for CRC, but this was not statistically significant (OR 4.00; 95% CI 0.80-38.67; P=0.11).
  
  
  CONCLUSIONS
  We found that having a colonoscopy for an indication of surveillance or screening is associated with decreased risk of CRC in the setting of Crohn's colitis. These data underscore the importance of CRC surveillance for Crohn's colitis in addition to ulcerative colitis and should prompt further study in this area.
authors.affiliation: Section of Gastroenterology and Hepatology, Inflammatory Bowel Disease Center, Dartmouth Medical School, Lebanon, NH, and Gastrointestinal Unit, MGH Crohn's and Colitis Center, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
authors.forename: Corey A
authors.initials: CA
authors.lastname: Siegel
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Sands
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D015331:Cohort Studies; D003092:Colitis / Q000150:complications* / Q000175:diagnosis; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D003424:Crohn Disease / Q000150:complications* / Q000175:diagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors