Risks and clinical features of colorectal cancer complicating Crohn's disease in Japanese patients

Background and Aim: No reports on the relative risk of development of colorectal cancer (CRC) in Japanese patients with Crohn's disease (CD) have been published. The present study aimed to investigate the relative risk and the clinical features of CRC complicating CD among patients managed at Fukuoka University Chikushi Hospital, Fukuoka, Japan (a tertiary referral center for inflammatory bowel diseases). Methods: The clinical backgrounds were analyzed of 512 patients with CD who have been treated by our department during the last 20‐year period (1985–2005) (total 6212.6 person years at risk). The standardized incidence ratio (SIR) refers to the relative risk of CRC in the subjects as compared with that in a sex‐ and age‐matched healthy population. Results: There were six cases with CRC. The SIR was significantly higher (3.2‐fold higher; 95% confidence interval, 1.2–6.9 P < 0.05) in the CD group than in the healthy population. The significant risk factors identified were female sex, mixed small and large bowel type, observation period over 20 years, onset of CD at less than 25 years of age, presence of anal disease, and positive history of surgery. The prognosis for the six cases with CRC was very poor (five cases died within 1.5 years). Conclusion: The risk of CRC in longstanding CD in Japan was similar to that in Western countries. The necessity of surveillance in the management of CD would also need to be discussed in the near future, especially in CD patients with anal lesions or fistulae, and are particularly important in patients with a 20‐year or more history of CD.