Prevalence and characteristics of sessile serrated lesions with dysplasia in Dutch fecal immunochemical test-positive screenees.

Background: Sessile serrated lesions (SSLs) with dysplasia (SSLDs) are considered high-risk polyps. We aimed to provide robust epidemiologic data on SSLDs over time in screening individuals with positive fecal immunochemical tests (FITs). Methods: All colonoscopy and pathology data of FIT-positive screenees in the Dutch colorectal cancer screening program (2014-2023) were analyzed. Prevalence of SSLs and SSLDs was calculated, along with number needed to scope (NNS). Dysplasia rate within SSLs was calculated over time. Multivariable logistic regression evaluated the influence of age and sex on SSLD prevalence, and assessed patient and polyp characteristics associated with dysplasia at polyp level. Results: Among 516 193 FIT-positive screenees, 1 033 298 polyps were removed, including 76 771 SSLs, of which 7010 (9.1%) exhibited dysplasia. Overall prevalence was 9.7% (95%CI 9.6-9.8) for SSLs and 1.1% (95%CI 1.1-1.1) for SSLDs. NNS to detect one SSL decreased over time, from 13 (2014-2018) to 9 (2019-2023), while NNS for SSLD remained stable at 90. The proportion of SSLDs declined from 17.5% in 2014 to 6.6% in 2023. Increasing age was associated with a higher SSLD prevalence (odds ratio per year 1.03; 95%CI 1.03-1.04) and dysplasia was more frequent in larger polyps (P < 0.001); however, 64.4% of SSLDs were <10 mm in size. Conclusions: This study showed a 1.1% prevalence of SSLD in FIT-positive screenees, offering valuable reference data. The finding that most SSLDs (64%) were small underscores the need to carefully assess small serrated polyps for dysplasia to ensure appropriate resection.