Post-polypectomy Surveillance Interval In High-risk Subjects After Screening Colonoscopy (PPSHR).

The aim of the study is to determine whether the risk of metachronous advanced neoplasia increases if surveillance interval was beyond the current recommendation of 3 years for high-risk subjects with advanced adenoma polyp at screening colonoscopy.

With many countries initiating population colorectal cancer (CRC) screening, including Hong Kong, more robust guidance for surveillance interval is required to maximize subject's benefit with optimal use of resources. Surveillance interval after removal of advanced adenoma at screening colonoscopy remains unclear. The current recommendation of 3-year is based on data collected before widespread implementation of population screening programs and quality metrics in colonoscopy. These high-risk subjects are those most likely to benefit from surveillance and represent the majority of the demand in surveillance colonoscopies.

The investigators hypothesize that the risk of metachronous advanced neoplasia significantly increases if surveillance interval was prolonged beyond 3 years for high-risk subjects. If such is true, our study's findings will provide definitive evidence to existing guidelines and the future Hong Kong population CRC screening programme of setting surveillance interval at 3-year. Conversely, if our study shows that there is no significant increase in risk beyond 3-year surveillance interval, an extended interval of 5-year is justified.