Guidelines for Familial Adenomatous Polyposis (FAP): challenges in defining clinical management for a rare disease.

Recent updated management guidelines for Familial Adenomatous Polyposis (FAP) have been published by professional bodies internationally. These recommendations reflect the diverse needs and capabilities of varying health systems worldwide, including thresholds for intervention and population health priorities. Whilst guidelines are closely aligned in many regards, there are areas of disparity. However, alongside discrepancies in guideline recommendations, common challenges also face professional bodies across the globe. Generation of a robust evidence-base in the environment of limited data is difficult in rare diseases such as FAP, underscored by the fact that expert consensus opinion underpins virtually all guidelines. The presence of a wide phenotypic spectrum in FAP and the other hereditary gastrointestinal polyposis syndromes, whilst now well recognised, further complicates the creation of universal recommendations. In this review we draw comparison between the various international guidelines for the management of FAP, using examples to focus on thematic areas of agreement and divergence. However, beyond this, we also wish to highlight the persisting evidence gaps in clinical management, and any areas of ongoing debate among clinicians, where we are yet to establish the optimal approach.