Long-term outcomes of pouch surveillance and risk of neoplasia in familial adenomatous polyposis.

Background Long-term pouch surveillance outcomes for familial adenomatous polyposis (FAP) are unknown. We aimed to quantify surveillance outcomes and to determine which of selected possible predictive factors is associated with pouch dysplasia. Methods We performed retrospective analysis of collected data on 249 patients. We analysed potential risk factors for developing adenomas or advanced lesions (≥10mm/high grade dysplasia (HGD)/cancer) in the pouch body (PB) and cuff using Cox proportional hazards models. Kaplan-Meier analyses included landmark 'time-point' analyses at 10 years after surgery to predict future risk of advanced lesions. Results Of 249 patients, 75% developed ≥ 1 PB adenoma. Sixteen percent developed an advanced PB lesion; 18% developed an advanced cuff lesion. Kaplan-Meier analysis showed a 10-year lag before most advanced lesions developed in the PB or cuff; cumulative incidence of 2.8% and 6.4% at ten years in PB and cuff, respectively. Landmark-analysis suggested that presence of adenomas prior to the 10-year point is associated with subsequent development of advanced lesions in the PB [HR 4.8 (1.6-14.1), P=0.004] and cuff [HR 6.8 (2.5-18.3), p<0.001]. There were two HGD and four cancer cases in the cuff and one PB cancer; all cases of cancer/HGD which had prior surveillance were preceded by 10mm adenomas. Conclusions Pouch adenoma progression is slow and most advanced lesions occur after ten years. High grade dysplasia and cancer were rare events. Pouch phenotype in the first decade is associated with future risk of developing advanced lesions and may guide personalised surveillance beyond ten years.