Patients with familial adenomatous polyposis (FAP) develop duodenal adenomatous polyps, whose risk of malignant progression increases with advancing Spigelman stage. However, prophylactic duodenal surgery carries substantial morbidity and mortality. 

This study aimed to evaluate the efficacy and safety of endoscopic treatment in FAP patients classified as Spigelman stages III-IV.

A retrospective analysis was conducted on patients who underwent endoscopic duodenal surveillance and treatment at a tertiary referral center between 2013 and 2025. Cold-snare polypectomy (CSP) and endoscopic mucosal resection (EMR) were the resection techniques employed. Data were collected on patient characteristics, polyp features, endoscopic procedures, histological findings, and Spigelman stage and score. 

Between 2013 and 2025, 1035 EGDs were performed in 247 patients (55% male, median age 47 years, IQR 33-57) at out center, with a median follow-up of 84 months (IQR 49-115). Duodenal non-ampullary adenomas were detected in 130 patients (52.6%). Their Spigelman stage distribution was: 31 (23.8%) stage I, 44 (33.9%) stage II, 22 (16.9%) stage III, and 33 (25.4%) stage IV.

Among patients with advanced Spigelman stages, thirty-five (74% male, median age 53 years, IQR 40-60), 17 classified as stage IV and 18 as stage III, underwent endoscopic treatment for duodenal polyps. During a median follow-up of 32 months (IQR 17–90), 268 polyps were resected in 122 endoscopic procedures (57% CSP). The median polyp size was 10 mm (IQR 7-10.5), 76.5% of resected polyps were located in the descending duodenum, and 17.5% harbored high-grade dysplasia. After therapeutic work-up, 69% of patients achieved downstaging of baseline Spigelman stage (p < 0.001). The median Spigelman score decreased from 8 (IQR 8–9) to 6 (IQR 5–8) (p < 0.001), while the proportion of patients with high-grade dysplasia declined from 74.3% to 5.7% (p < 0.001). Kaplan-Meier analysis showed median times to re-progression and re-treatment after the first endoscopic treatment of 42 and 45 months, respectively. 

No major adverse events occured. One patient required surgery for multiple high-grade dysplasia adenomas not amenable to endoscopic resection, and no duodenal cancer were observed during the study period.

Endoscopic treatment proved to be safe and effective in downstaging both Spigelman score/stage and histological dysplasia severity, thereby reducing the need for prophylactic surgery in FAP patients with advanced duodenal disease. Given the risk of re-progression in this setting, multiple endoscopic resections are often required to achieve long-term disease control.