Gastric polyposis and risk of gastric cancer in patients with familial adenomatous polyposis.

Background: Gastric polyposis is common in familial adenomatous polyposis (FAP) syndrome. However, the incidence and risk factors for gastric cancer (GC) are unclear. We aimed to evaluate the incidence of GC and associated risk factors in a large FAP population.

Methods: Retrospective review of patients with FAP undergoing upper endoscopy at Mayo Clinic from 1989 to 2023. Cumulative incidence of GC (95% CIs) were calculated using Kaplan-Meier survival approaches. Associations of clinical characteristics with development of GC were examined using Cox proportional hazards regression.

Results: A total of 337 patients underwent 2502 endoscopies with a median of 10.4 years (IQR, 3.9-17.2) of endoscopic surveillance. At any time during surveillance, 294 patients (87%) had gastric polyps; 200 (59%), fundic gland polyps; 116 (34%), low-grade dysplasia (LGD); and 11 (3.3%), high-grade dysplasia (HGD). Among these, only 6 patients (2%) developed GC-5 with HGD (3 [50%] on previous endoscopy and 2 [33%] at the time of cancer diagnosis) and 1 (16%) with LGD on previous endoscopy. The 10-year cumulative incidence of GC is 0% with no polyps, 1% with polyps, 6% with LGD, 11% with polyps ≥2 cm, and 20% with HGD. Both HGD and polyps ≥2 cm had a strong association with the development of GC (P < .001).

Conclusion: Although the overall risk of GC in FAP is low, outcomes remain poor. GC can be predicted by endoscopic findings and specific GC surveillance guidelines are imperative to improve detection rates and guide timely intervention.