Traditional Serrated Adenomas Associated With Risk of Subsequent High-Risk Polyps and Colorectal Cancer

Traditional serrated adenoma (TSA) is a rare yet established precursor to colorectal cancer (CRC). The risk of colorectal neoplasia after TSA removal remains unclear.

We identified participants without polyps or with TSAs during index colonoscopy from the Mass General Brigham Colonoscopy Cohort (2007-2023). Participants were prospectively followed for recurrence of high-risk polyps and incidence of CRC. We used the time-varying multivariable-adjusted Cox proportional hazards model to estimate the risk of CRC and high-risk polyps associated with baseline diagnosis of TSAs.

We identified 109,218 participants without polyps and 252 with TSAs, of whom 35,124 (32%) and 139 (55%) had undergone a follow-up colonoscopy, respectively. TSAs were predominantly located in the distal colon (35%) and rectum (38%), with approximately half sized <10 mm. TSAs tended to demonstrate as a single lesion (84%) but coexist with other types of polyps (70%). Compared with participants without polyps, those with TSAs had higher risk of developing high-risk polyps, high-risk adenomas, high-risk serrated polyps, and CRC, with the hazard ratio (95% confidence interval) of 3.31 (2.35-4.66), 3.07 (2.12-4.44), 6.66 (3.79-11.71), and 7.23 (2.23-23.44), respectively. The risk elevation of high-risk polyps peaked at 3 years post-TSA removal (hazard ratio = 10.85, 95% confidence interval, 6.36-18.52). Among recurrent polyps after TSA removal, 54% (52/96) occurred in the proximal colon and 69% (66/96) was serrated polyps.

Patients with TSA removal had an elevated risk of colorectal neoplasia, particularly within 3 years after TSA removal, supporting the current US recommendations for a surveillance colonoscopy at 3 years.