Crohn's disease is associated with small bowel cancer whilst risk of colorectal cancer is less clear. To ascertain the combined estimates of relative risk of these cancers in Crohn's disease. MEDLINE was searched to identify relevant papers. Exploding references identified additional publications. When two papers reviewed the same cohort, the later study was used. Meta-analysis showed overall colorectal cancer relative risk in Crohn's disease as 2.5 (1.3-4.7), 4.5 (1.3-14.9) for patients with colonic disease and 1.1 (0.8-1.5) in ileal disease. Meta-regression showed reduction in relative risk over the past 30 years. Subgroup analysis showed Scandinavia had significantly lower colorectal cancer relative risk than the UK and North America. Cumulative risk analysis showed 10 years following diagnosis of Crohn's disease relative risk of colorectal cancer is 2.9% (1.5%-5.3%). Meta-analysis showed small bowel cancer relative risk in Crohn's disease is 33.2 (15.9-60.9). Small bowel cancer relative risk has not significantly reduced over the last 30 years. Relative risk of colorectal and small bowel cancers are significantly raised in Crohn's disease. Cumulative risk of colorectal cancer of 2.9% at 10 years suggests a potential benefit from routine screening. However, the value of screening requires rigorous appraisal.
