Abstract
Uncertainty prevails about the magnitude of excess risk of small bowel cancer in patients with inflammatory bowel disease (IBD). To quantify the risk of small bowel adenocarcinoma and neuroendocrine tumors in patients with ulcerative colitis (UC) and Crohn's disease (CD), we undertook a population-based cohort study of all patients with IBD diagnosed in Norway and Sweden from 1987 to 2016. Patients were followed through linkage to national registers. We calculated standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) of small bowel adenocarcinomas and neuroendocrine tumors for patients with CD and UC. We excluded the first year of follow-up to reduce reverse causality. Among 142008 patients with a median follow-up of 10.0 years, we identified 66 adenocarcinomas and 57 neuroendocrine tumors in the small bowel. The SIR of small bowel adenocarcinoma was 8.3 (95% CI 5.9-11.3) in CD and 2.0 (95% CI 1.2-3.1) in UC. The incidence rates of adenocarcinomas were highest in CD with stricturing disease and extent limited to the small bowel, at 14.7 (95% CI 8.2-24.2) and 15.8 (95% CI 8.4-27.0) per 100000 person-years, respectively. The SIR of neuroendocrine tumors was 2.5 (95% CI 1.5-3.9) in CD and 2.0 (95% CI 1.4-2.8) in UC. Patients with CD experienced an eightfold increased risk of small bowel adenocarcinomas, patients with both UC and CD experienced an about twofold increased risk of neuroendocrine tumors, and patients with UC experienced a twofold increased risk of small bowel adenocarcinoma. The small absolute excess cancer risk suggests that active surveillance to diagnose small intestinal cancer early is unlikely to be cost-effective.
Highlights
Proper, individualized surveillance of cancer risk in patients with inflammatory bowel disease (IBD) requires valid risk prediction
Our most salient findings were an about eightfold increased risk of adenocarcinoma in Crohn’s disease (CD) and twofold in ulcerative colitis (UC), with a higher excess risk among those diagnosed with IBD before age 40 years; and some evidence of increased risk in CD after >10 years of follow-up
The risk of neuroendocrine tumors was increased by about twofold in patients with both CD and UC, and it was seemingly confined to CD affecting the small bowel and to extensive colitis
Summary
Proper, individualized surveillance of cancer risk in patients with inflammatory bowel disease (IBD) requires valid risk prediction. Volume 33 - Issue 6 - 2022 fundamental problem arises because symptoms of IBD may be so mild that the diagnosis is not confirmed until a cancer has already become symptomatic Needless to say, this introduces selection bias because patients with a prevalent cancer are overrepresented at enrollment into any cohort study, which is often reflected in the highest excess risk during early follow-up. This introduces selection bias because patients with a prevalent cancer are overrepresented at enrollment into any cohort study, which is often reflected in the highest excess risk during early follow-up This bias precludes any valid quantification of risk and assessment of the temporal relationship between IBD onset and cancer diagnosis. Uncertainty prevails about the magnitude of excess risk of small bowel cancer in patients with inflammatory bowel disease (IBD).
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