Extracolonic Cancer Risk After Total Colectomy for Inflammatory Bowel Disease: A Population-based Cohort Study.

Background: Patients with inflammatory bowel disease are at increased risk of extracolonic cancers. Little is known regarding this risk following total colectomy [TC].
Methods: Patients who underwent TC for inflammatory bowel disease in Denmark during 1977-2013 were identified from the Danish National Patient Registry. Incidence rates of extracolonic cancers were determined through record linkage to the Danish Cancer Registry and compared with expected incidence rates in the general population. Standardized incidence ratios [SIRs] were calculated as the observed vs expected cancer incidence.
Results: In total, 4430 patients (3441 with ulcerative colitis [UC]; 989 with Crohn's disease [CD]) were followed for 54,183 person-years after TC. Following their surgery, 372 patients were diagnosed with extracolonic cancer compared to 331 expected [SIR = 1.1 (95% confidence interval {CI}: 1.0-1.2)]. The risk of extracolonic cancer overall was increased among patients with CD and TC (SIR = 1.5 [95% CI: 1.2-1.8]), but not among patients with UC and TC (SIR = 1.0 [95% CI: 0.9-1.2]). Patients with UC and TC had a higher risk of intestinal extracolonic cancer (SIR = 2.0 [95% CI: 1.4-2.7]). Patients with CD and TC had a higher risk of smoking-related cancers (SIR = 1.9 [95% CI: 1.2-2.9]), intestinal extracolonic cancer (SIR = 3.1 [95% CI: 1.6-5.5]) and immune-mediated cancers (SIR = 1.5 [95% CI: 1.0-2.1]).
Conclusion: Patients with CD and TC had a higher risk of extracolonic cancer overall compared to the general population, while patients with UC and TC did not. Site-specific cancer risk varied according to inflammatory bowel disease type.
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