Risk of Colorectal Cancer and Dysplasia in Asian Ulcerative Colitis Patients

Background.Several studies have shown an increased risk of small bowel adenocarcinoma (SBA) in patients with Crohn's disease (CD).However, SBA occurs in patients with a small bowel CD.The standardized incidence ratio (SIR) of SBA should therefore be calculated in this particular category of patients.We assessed this risk in a prospective observational cohort study.Methods.19 486 patients with inflammatory bowel disease, of whom 11 759 (60.3%) had CD and 7 727 (39.7%) had ulcerative colitis or unclassified inflammatory bowel disease, were enrolled in a nationwide French cohort by 680 gastroenterologists, who reported details of immunosuppressive therapy during the observation period, cases of cancer, and deaths.A SBA risk was obtained by dividing the observed cases in our cohort to the expected cases in the general population, obtained by multiplying the patient-years at risk in each 5-year age group by the corresponding sex-specific and age-specific incidence rate for 2005, provided by the French Cancer Registries database (FRANCIM).Findings.Median follow-up was 35 months (IQR 29-40), consisting in 30411 person-years for CD patients.At baseline, 8222 (69.9%) patients had small bowel CD (either alone or associated with colonic CD), which corresponds to 21 316 patient-years.Five new cases of SBA were diagnosed, all in patients with small bowel CD.The incidence rates of SBA were 0.16 per 1000 (95% CI 0.05-0.35)patient-years among CD patients, and 0.234 per 1000 (95% CI 0.076-0.547)patient-years among small bowel CD patients.SIR of SBA were 21.0 (95% CI 6.83-49.1,p<0.01) and 34.9 (95% CI 11.3-81.5,p<0.01) for CD and small bowel CD respectively.Conclusion.In this prospective study, patients with small bowel CD had a SIR of 34.9 of SBA.