Metachronous Colorectal Neoplasia in Young Adults With Advanced Neoplasia Undergoing Colonoscopy: A Comparison of Risk by Age <45 Years Versus 45 to 49 Years.

Background: The risk of metachronous advanced colorectal neoplasia (mACRN) in young adults with advanced lesions at baseline colonoscopy is not well defined.

Aims: To examine the risk for (mACRN) in adults <50 years old who had advanced neoplasia (AN) at baseline colonoscopy and determine factors associated with mACRN in these patients.

Method: Patients 18 to 49 years of age with ≥1 AN [tubular adenoma (TA) ≥10 mm or with villous features or high-grade dysplasia (HGD), sessile serrated lesion (SSL) ≥10 mm or with dysplasia, traditional serrated adenoma (TSA)] on baseline colonoscopy between 2011 and 2021 who had surveillance colonoscopy >6 months after their baseline examination were included. Outcomes were assessed based on age at baseline colonoscopy, <45 years versus 45 to 49 years, and by follow-up colonoscopy findings: (1) normal, (2) nonadvanced neoplasia (NAN), and (3) AN.

Results: Three hundred sixty-six patients with AN underwent ≥1 surveillance colonoscopy: 310 (84.7%) <45 years versus 56 (15.3%) 45 to 49 years. The mean follow-up time was longer for the <45-year-olds versus the 45 to 49-year-olds (43±26.4 vs. 28.4±12.8 mo respectively, P<0.001). The absolute risk of mACRN was 13.5% in the <45 age group versus 16.1% in the 45 to 49 age group, P=0.28. The 3-year cumulative incidence rates of mACRN were comparable for patients <45 and 45 to 49 years old: 10% (95% CI: 10% to 42%) versus 20% (95% CI: 7% to 15%), P=0.065. BMI was the only risk factor associated with mACRN OR 1.045 [95% CI (1.001 to 1.09)].

Conclusions: In our cohort of patients <50 years old with AN at baseline, mACRN occurred at a similar rate to that reported by guidelines in 50 years and older, suggesting that current recommended post polypectomy surveillance is appropriate for this age group. BMI was independently associated with mACRN. Future studies should examine how weight management in patients with high BMI mitigates the recurrence of advanced neoplasia.