Risk of cancer and reoperation after ileorectal anastomosis and ileal pouch-anal anastomosis in familial adenomatous polyposis

Objectives: To prevent colorectal cancer (CRC), most patients with familial adenomatous polyposis (FAP) undergo (procto)colectomy with ileorectal anastomosis (IRA) or ileal pouch-anal anastomosis (IPAA). After surgery, these patients remain at risk of developing cancer in the remnant rectum or rectal cuff/pouch. We aimed to compare the long-term risk of cancer following IRA or IPAA in FAP. Methods: We performed an international multicenter historical cohort study of FAP patients undergoing IRA or IPAA from 1990 to 2023. The proportion of patients developing cancer following surgery was estimated using the Kaplan-Meier method. Results: (Procto)colectomy was performed in 685 patients (53.6% female); 366 (53.4%) had IRA and 319 (46.6%) IPAA. Median age at IRA and IPAA was 23 and 27 years, and median follow-up was 12 and 15 years, respectively. Overall, 8 patients (2.2%) developed rectal and/or rectal cuff/pouch cancer after IRA and 0.9% after IPAA. The estimated 10- and 20-year cancer incidence after IRA vs IPAA were 1.6% vs 0.4% and 2.5% vs 0.9%, respectively (log-rank p=0.15. Reoperations, mainly for extensive polyposis, were performed in 39 (10.7%) patients with an IRA and 24 (7.5%) patients following IPAA. The number of post-operative endoscopic surveillance endoscopies was higher in patients with an IRA compared to those with an IPAA (p<0.001). Conclusions: Over the last three decades, few patients were diagnosed with cancer in the rectum or rectal cuff/pouch after (procto)colectomy in FAP. This might be due to an improved selection of the type of (procto)colectomy and close endoscopic surveillance including prophylactic polypectomies.