Comparative risk of high-risk neoplasia after polypectomy among individuals aged below 50 years versus 50 years and older

Background Limited evidence supports colonoscopy surveillance practices among individuals aged <50 years. Objective To compare the risk of polyp recurrence and colorectal cancer (CRC) among young and old adults after polypectomy. Design We prospectively examined the risk of metachronous high-risk neoplasia, including high-risk adenoma, high-risk serrated polyp (SP) and CRC, according to index colonoscopy findings among individuals aged <50 years and ≥50 years who had received ≥1 follow-up colonoscopy in the Mass General Brigham Colonoscopy Cohort (2007–2023). We used a multivariable-adjusted Cox proportional hazards model to calculate HRs. Results We identified 37 576 adults without polyps, 26 693 with adenomas and 15 425 with SPs (including 8303 with synchronous adenomas and SPs). Among these 10 977 (29.2%), 3385 (12.7%) and 2659 (17.2%) were diagnosed before age 50 years, respectively. The associations between index polyp findings and subsequent risk of high-risk neoplasia were stronger for age <50 years than ≥50 years; however, such differences disappeared (P heterogeneity >0.05) once the analysis was restricted to index colonoscopy for screening purposes only. Among screened individuals, in both age groups, the association was particularly strong for individuals with index high-risk lesions and peaked at 3 years after polypectomy, with HRs (95% CI) of 4.60 (3.63 to 5.84) and 5.59 (3.89 to 8.03) for young adults with index high-risk adenoma and high-risk SPs, respectively. Conclusion Patients undergoing polypectomy at a screening colonoscopy below age 50 years exhibited a similarly increased risk of metachronous neoplasia as those aged ≥50 years, suggesting that current surveillance guidelines developed in old adults may apply to young adults.