Rationale and design of the European Polyp Surveillance (EPoS) trials

Background: Current guidelines recommend surveillance colonoscopies after polyp removal depending on the number and characteristics of polyps, but there is a lack of evidence supporting the recommendations. This report outlines the rationale and design of two randomized trials and one observational study investigating evidence-based surveillance strategies following polyp removal. Study design and endpoints: The EPoS studies started to recruit patients in April 2015. EPoS study I randomizes 13 746 patients with low-risk adenomas (1-2 tubular adenomas size <10mm, low-grade dysplasia) to surveillance after 5 and 10 years, or 10 years only. EPoS study II randomizes 13704 patients with high-risk adenomas (3-10 adenomas or adenoma >= 10mm in diameter, or adenoma with high-grade dysplasia, or >25% villous features) to surveillance after 3, 5, and 10 years, or 5 and 10 years only. EPoS study III offers surveillance after 5 and 10 years to patients with serrated polyps >= 10mm in diameter at any location, or serrated polyps >= 5mm in diameter proximal to the splenic flexure. All polyps are removed before patients enter the trials. The primary end point is colorectal cancer incidence after 10 years. We assume a colorectal cancer risk of 1% for patients in EPoS I, and 2% for patients in EPoS II. Using a noninferiority hypothesis with an equivalence interval of 0.5% for EPoS I and 0.7% for EPoS II, the trials are 90% powered to uncover differences larger than the equivalence intervals. For EPoS III, no power analyses have been performed. Conclusions: The present trials aim to develop evidence-based strategies for polyp surveillance, thereby maximizing effectiveness and minimizing resources.