Development of Desmoid Tumors After Ileorectal Anastomosis Versus Ileal Pouch-Anal Anastomosis in Familial Adenomatous Polyposis

Background & Aims: Desmoid tumors (DT) are an important cause of morbidity and mortality in patients with familial adenomatous polyposis (FAP). DT development might be related to the type and approach of colectomy. We aimed to compare DT development after colectomy with ileorectal anastomosis (IRA) and proctocolectomy with ileal pouch-anal anastomosis (IPAA). Methods: We performed an international historical cohort study in patients with FAP who underwent IRA or IPAA between 1961 and 2020. The primary outcome was the incidence of abdominal DT (either mesenteric, retroperitoneal, or abdominal wall). Patients with a DT diagnosis before or at colectomy were excluded. Time to DT was considered censored at an eventual secondary proctectomy after IRA. We used multivariable Cox regression modelling to adjust for potential confounders. Results: We analyzed data from 852 patients: 514 after IRA and 338 after IPAA (median follow-up, 21 and 16 years, respectively). DTs were diagnosed in 64 IRA patients (12%) and 66 IPAA patients (20%). The cumulative DT incidence at 5 and 10 years was 7.5% and 9.3% after open IRA and 4.7% and 10.9% after laparoscopic IRA. These estimates were 13.6% and 15.4% after open IPAA and 8.4% and 10.0% after laparoscopic IPAA. The postoperative risk was significantly higher after IPAA (P < .01) in multivariable analysis, whereas approach did not significantly influence the risk. Conclusions: The risk of developing an abdominal DT was found to be significantly higher after IPAA than after IRA. Postoperative DT risk should be taken into account when choosing between IRA and IPAA in FAP.