Incidence of Interval Colorectal Cancer Among Inflammatory Bowel Disease Patients Undergoing Regular Colonoscopic Surveillance

Background & aims: Surveillance is recommended for patients with long-term inflammatory bowel disease because they have an increased risk of colorectal cancer (CRC). To study the effectiveness of surveillance, we determined the incidence of CRC after negative findings from surveillance colonoscopies (interval CRC).

Methods: We collected data from 1273 patients with ulcerative colitis or Crohn's disease, enrolled in a surveillance program at 7 hospitals in The Netherlands, who underwent 4327 surveillance colonoscopies from January 1, 2000, through January 1, 2014. Patients were followed up from their first surveillance colonoscopy until the last surveillance colonoscopy, colectomy, or CRC. Factors that might have contributed to the occurrence of CRC were categorized as inadequate procedures (ie, inadequate bowel preparation), inadequate surveillance (CRC occurring outside the appropriate surveillance interval), or inadequate management of dysplasia (CRC diagnosed in the same colonic segment as a previous diagnosis of dysplasia). The remaining CRC cases were classified as true interval CRCs.

Results: CRC was diagnosed in 17 patients (1.3%), with an incidence of 2.5 per 1000 years of follow-up evaluation. Factors that might account for the occurrence of CRC were identified in 12 patients (70%). These were inadequate colonoscopies in 4 patients (24%), inadequate surveillance intervals in 9 patients (53%), and inadequate management of dysplasia in 2 patients (12%). The remaining 5 cases of CRC (30%) were classified as true interval CRCs.

Conclusions: In a retrospective analysis of patients with inflammatory bowel disease participating in a surveillance program, the incidence of CRC was only 1%, which supports the implementation of longer surveillance intervals. However, the fact that 30% of CRC cases were interval cancers indicates the need for variable surveillance intervals based on risk factors for CRC.