Background: The adenoma detection rate (ADR) has long been used as a target by endoscopists for colorectal cancer (CRC) screening in the general population. However, ADRs in higher-risk populations have not been well established, including Lynch syndrome (LS), which is the most common hereditary cause of CRC. Having colorectal neoplasia rate benchmarks in LS is important for endoscopists performing surveillance colonoscopies in these high-risk individuals. Therefore, the aim of this study is to determine the ADR in addition to the overall colorectal neoplasia detection rate (CNDR), CRC detection rate (CRCDR), and proximal serrated detection rate (PSDR), in a cohort of individuals with LS.

Methods: We performed a retrospective study of all individuals with LS who were evaluated at a single tertiary care center from May 2001 to September 2023 (n = 542). We excluded individuals without a completed colonoscopy/flex-sig on record within the study time period and excluded all colonoscopies/flex-sigs completed at outside centers. Data from colonoscopy/flex-six procedures and pathology reports was collected along with other relevant demographic, personal health history, and family history data. CNDR was defined as the rate that a CRC, adenoma, or serrated lesion proximal to the sigmoid colon was identified. A Fisher Exact Test and Kruskal-Wallis Test were used to assess factors associated with colorectal neoplasia.

Results: Amongst 542 individuals with LS, 190 were excluded because they did not have an in-house colonoscopy/flex-sig on file, leaving 352 individuals with 1,296 colonoscopies included in our analysis. This cohort was primarily female (64.5%), white (87.5%), with private insurance (76.1%), and there was a near-even distribution across different genotypes (Table 1). We found a CNDR of 27.9%, CRCDR of 1.5%, ADR of 21.4%, and PSDR of 7.7% (Figure 1). Advanced age, Medicare insurance, history of prior colonic resection, and prior history of a non-CRC were significantly associated with colorectal neoplasia (p < 0.05). Colorectal neoplasia was not associated with genotype, biological sex, race, smoking status, BMI, aspirin use (≥2 years), or family history (p > 0.05).

Conclusion: Despite getting more frequent colonoscopies/flex-sigs, individuals with LS still had a high colorectal neoplasia rate, primarily driven by the detection of colonic adenomas. These colorectal neoplasia rates may serve as helpful “ballpark rates” for those performing colonoscopy/flex-sig in patients with LS. However, further studies are needed to determine whether colorectal neoplasia detection rates amongst endoscopists are predictive of CRC risk and outcomes in LS.

Danielle Mirda

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