Objectives To estimate the overall risk of cancer in a population-based cohort of patients with inflammatory bowel disease (IBD) and how IBD-related medications modify this risk. Methods We identified all incident cancers (excluding nonmelanoma skin cancer) after IBD diagnosis in a cohort of 839 patients diagnosed as having IBD from January 1, 1940, through December 31, 2004, in Olmsted County, Minnesota, and followed up for a median 18 years through December 31, 2011 (122 patients taking biologic agents at last follow-up). We calculated standardized incidence ratios (SIRs) with 95% CIs of all cancers and compared cancer risk in patients treated with immunomodulators (IMMs) and biologics with that of patients not exposed to these medications, using an incidence rate ratio (IRR). Results One hundred nine patients developed 135 cancers. The 10-year cumulative probability of cancer was 3.8%. Patients with Crohn disease (SIR, 1.6; 95% CI, 1.2-2.1) but not ulcerative colitis (SIR, 1.1; 95% CI, 0.8-1.4) had an increased overall risk of cancer compared with the general population. Patients treated with IMMs (relative to IMM-naive patients) had an increased risk of melanoma (IRR, 5.3; 95% CI, 1.1-24.8) (and a numerically higher risk of hematologic malignant tumors [IRR, 4.2; 95% CI, 0.9-19.2]), although this risk returned to baseline on discontinuation of IMM treatment. Patients treated with biologics (relative to biologic-naive patients) had a numerically higher risk of hematologic malignant tumors (IRR, 5.3; 95% CI, 0.7-40.5). There was no significant increase in the risk of gastrointestinal malignancies in patients with IBD compared with the general population. Conclusions We observed an increased risk of melanoma in IMM-treated patients with IBD, and this risk returned to baseline after discontinued use of the medications.
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