Endoscopic indicators in patients with familial adenomatous polyposis undergoing duodenal resections – a nationwide Danish cohort study with long-term follow-up

Abstract Background: Familial adenomatous polyposis (FAP) predisposes individuals to duodenal adenomas. This study describes the histopathological features of endoscopic and surgical specimens from the duodenum, as well as genotype-phenotype associations. Methods: All known FAP patients were included from the Danish Polyposis Register. FAP patients were defined as having more than 100 cumulative colorectal adenomas and/or having a known germline pathogenic variant in the APC gene. Endoscopic procedures, histopathology, and genetics were evaluated. Results: Of 500 FAP patients, 70.6% underwent esophagogastroduodenoscopy (EGD) at least once. Of these, 59.2% presented with detectable duodenal adenomas. The most severe morphology was tubular in 62.7% patients, tubulovillous in 25.4%, and villous in 12.0%, while the most severe dysplasia was low-grade in 67.5% patients, high-grade in 25.4%, and 6.7% had adenocarcinoma. In 6.2% of FAP patients, duodenal resection was recommended, including 29% with duodenal adenocarcinoma. The risk of duodenal surgery was 1.31 per 1,000 person-years (median age: 53 years). The predominant reason for surgery was extensive polyposis (67.7%). Of the patients who underwent duodenal resection, a median of six (IQR: 4–8) EGDs were performed within five years prior to surgery, but 67.6% and 83.9% never underwent a duodenal polypectomy or endoscopic mucosa resection, respectively. Of note, seventeen of 500 patients (3.4%) developed duodenal adenocarcinoma, of which 47% were advanced at diagnosis. Genetic evaluations revealed various pathogenic variants in the APC gene, with no strong genotype-phenotype association. Conclusions: The prevalence of duodenal adenomas and cancer in FAP warrants vigilant endoscopic surveillance. Nevertheless, the need for duodenal surgery persists and should together with endoscopic practice be monitored in national registers.