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Prevalence of Sessile Serrated Lesions in Individuals With Positive FIT Results Undergoing Colonoscopy
abstract
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Access this abstract now Full Text Available for ClinicalKey SubscribersSessile serrated lesions (SSLs) are important precursors to colorectal cancer (CRC). It is estimated that 20-30% of CRCs arise from SSLs through a pathway distinct from the traditional adenoma-carcinoma sequence. The United States Multi-Society Task Force (USMSTF) on CRC recommends colonoscopy or fecal immunochemical test (FIT) as tier 1 tests for CRC screening in average risk individuals. While the current adenoma detection rate (ADR) in FIT-positive individuals has been estimated as 45% in men and 35% in women, the prevalence of SSLs in FIT-positive individuals is not widely known. The aim of our study is to determine the prevalence of detected SSLs in FIT-positive individuals using a nationwide database.
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Prevalence of Sessile Serrated Lesions in Individuals with Positive Fecal Immunochemical Test Undergoing Colonoscopy: Results from a Large Nationwide Veterans Affairs Database
Gastroenterology 2024 Feb 29;[EPub Ahead of Print], N Wilson, M Bilal, A Westanmo, A Gravely, A ShaukatFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
There is strong evidence that the sessile serrated lesion (SSL) pathway is an important precursor to the development of colorectal cancer (CRC). Analyses consistently find that post-colonoscopy cancers (compared with baseline CRCs) often have genetic characteristics of the SSL pathway, suggesting that such lesions may be missed at colonoscopy. Research about the natural history of SSLs has been challenging because of 1) difficulty identifying flat sessile lesions at colonoscopy and 2) misclassification of lesions by pathology. As colonoscopy quality has improved owing to digital imaging and quality metrics, and as pathology standardization has become more common, SSLs have been recognized in approximately 6.4% of screening colonoscopy exams.1
This new study by Wilson et al determines the rate of clinically significant SSLs in a cohort of veterans undergoing colonoscopy for a positive fecal immunochemical test (FIT) result. The rate of SSLs was 6.1%, slightly lower than published rates in patients with routine colonoscopy screening, suggesting that the finding is coincidental and not related to FIT. Just for perspective, the risks of advanced adenomas and CRC are at least two-fold higher in patients with a positive FIT result; hence, the recommendation for colonoscopy.
This study has several limitations. The population is largely (93.5%) male, comprising White individuals (74%) with relatively high rates of current smoking (33%) and, therefore, may not be representative of the general population. The data lack information about polyp size and location. Patients with large (>1 cm) or proximal polyps classified as hyperplastic were excluded; therefore, the true prevalence of SSLs may be somewhat underestimated.
Despite these limitations, what can we take away from this analysis? First, it appears that FIT positivity is not predictive of SSLs. This is not surprising given the phenotypic characteristics of SSLs — namely flat sessile lesions without prominent blood vessels. As the risk of advanced adenomas and CRC are strongly associated with positive FIT results, colonoscopy is recommended.
A second important finding is the time trend for SSL prevalence. This study spanned from 2012 to 2022, during which prevalence of SSLs increased from 4.6% to 8.2%. It is unlikely that this is a true change in prevalence, and is more likely owing to better detection at colonoscopy and more standardized pathology analysis. I think this means we are getting closer to the true prevalence of SSLs. I agree with the authors that we may be ready to establish a quality metric for SSL detection, similar to the adenoma detection rate (ADR).
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