title: Risk of colorectal cancer in relatives of patients with inflammatory bowel disease (Denmark)
abstract: OBJECTIVE
  It has been suggested that inflammatory bowel disease (IBD) and colon cancer are associated because they have genetic susceptibility in common, rather than IBD causing cancer. We examined the risk of colorectal cancer in first-degree relatives of patients with IBD in order to evaluate if they share the same genetic susceptibility.
  
  
  METHODS
  We identified patients with IBD in the Danish Hospital Discharge Registry. A cohort of all first-degree relatives to these patients were linked to the Danish Cancer Registry. Colorectal cancers observed were compared with expected values based on age, gender, and calendar-specific incidence rates in the general population.
  
  
  RESULTS
  Among 4,496 patients with IBD, a total of 19,645 relatives were identified. For parents of patients with Crohn's disease, we observed 19 cases of colorectal cancer compared with 20 expected (standardized incidence ratio [SIR] = 1.0, 95 percent confidence interval [CI] = 0.6-1.5). For parents of patients with ulcerative colitis, 55 cases were observed compared with 51 expected (SIR = 1.1, CI = 0.8-1.4).
  
  
  CONCLUSIONS
  The study did not corroborate the hypothesis that the same genetic factors play a significant role in the etiology of colorectal cancer and IBD, but more information is needed to disregard the possible link between IBD and colon cancer.
authors.affiliation: Danish Epidemiology Science Center at the Department of Epidemiology and Social Medicine, University of Aarhus.
authors.forename: K
authors.initials: K
authors.lastname: Fonager
authors.forename: H T
authors.initials: HT
authors.lastname: Sørensen
authors.forename: L
authors.initials: L
authors.lastname: Mellemkjaer
authors.forename: J H
authors.initials: JH
authors.lastname: Olsen
authors.forename: J
authors.initials: J
authors.lastname: Olsen
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D016001:Confidence Intervals; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000235:genetics*; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D016012:Poisson Distribution; D012042:Registries; D012307:Risk Factors; D017678:Sex Distribution; D015996:Survival Rate