The risk of extra-intestinal cancer in inflammatory bowel disease: a systematic review and meta-analysis of population-based cohort studies

BACKGROUND & AIMS: Patients with Crohn's disease (CD) and ulcerative colitis (UC) are at increased risk of developing intestinal cancer. However, less is known about the risk of extraintestinal cancers (EICs). The aim of this study was to conduct a systematic review and meta-analysis of population-based cohorts assessing the risk of EICs in inflammatory bowel disease (IBD) patients.

METHODS: Only population-based studies reporting on the prevalence or incidence of EICs were included. In total, 884 studies were screened and those included were assessed for quality. Eligible studies were pooled for length of follow-up evaluation, events in the IBD population, and events or expected events in a control population for the meta-analyses.

RESULTS: In total, 40 studies were included in the systematic review and 15 studies were included in the meta-analysis. The overall risk of EICs was found to be increased in both CD (incidence rate ratio [IRR]: 1.43 [CI, 1.26, 1.63]) and UC (IRR: 1.15 [1.02, 1.31]) patients. Both CD and UC patients presented with an increased risk of skin (IRR: CD, 2.22 [1.41-3.48]; UC, 1.38 [1.12-1.71]) and hepatobiliary (IRR: CD, 2.31 [1.25-4.28]; UC, 2.05 [1.52-2.76]) malignancies. Furthermore, CD patients showed an increased risk of hematologic (IRR, 2.40 [1.81-3.18]) and lung (IRR, 1.53 [1.23-1.91]) cancers. These increased risks were present despite treatment with immunosuppressives.

CONCLUSIONS: This systematic review and meta-analysis shows that both CD and UC patients are at an increased risk of developing EICs, both overall and at specific sites. However, additional studies with longer follow-up evaluation are needed to assess the true risk of EICs posed by IBD.