Surveillance Colonoscopy After Endoscopic Resection of Large Laterally Spreading Tumors (20 mm) Detects High-Risk Synchronous Lesions

Introduction: Patients with large laterally spreading tumors (adenomas ≥20 mm) are at increased risk for interval cancers. Current guidelines recommend surveillance colonoscopy within 6 months only after piecemeal endoscopic resection of lesions ≥20 mm to evaluate resection sites for local recurrence. Outcomes of surveillance colonoscopy in this high-risk population is largely unknown. The aim of this study was to determine the rate and characteristics of missed synchronous lesions in patients who underwent endoscopic resection of large laterally spreading tumors (LLSTs). Methods: This is a retrospective cohort study that included adult patients who were referred to a tertiary center for endoscopic resection of LLSTs (≥20 mm) from January 2017 to May 2022. To be included in the analysis, patients must have had a follow up surveillance colonoscopy within 18 months of the endoscopic resection of the large polyps. Patients with history of hereditary polyposis syndromes, inflammatory bowel disease, colon cancer, and colon resection or if the index polyp is not an adenoma, or sessile serrated polyp (SSP) were excluded. Logistic regression model was used for predictive factors of missed lesions using Stata 14. Results: Of a total of 456 patients who had undergone endoscopic resection of LLSTs, 250 patients (54.8%) had surveillance colonoscopy within 18 months. The average age was 65.5 years and 56% of the patients were male. Among them, 129 patients (51.6%) were found to have polyps on surveillance colonoscopy with a total of 333 missed lesions. One hundred and ninety (57.1%) missed lesions were found proximal to the splenic flexure. The missed lesions ranged from 1 mm to 50 mm in size. Two hundred and fifteen (64.6%) were diminutive (≤ 5mm). Most lesions were tubular adenomas (70.0%), followed by hyperplastic polyps (15.6%), SSPs (11.7%), and tubulovillous adenomas (1.2%). There were high-risk lesions, including 2 adenocarcinomas (0.6%), 51 advanced adenomas (15%) and 13 adenomas that were ≥20 mm in size (3.9%). In the multiple logistic regression analysis, we found that age was the only risk factor significantly associated with missed synchronous lesions (Figure 1, Table 1). Conclusion: Our study highlights the significant rate of missed, high-risk synchronous lesions in patients who underwent endoscopic resection of LLSTs. Our findings underscored the importance of surveillance colonoscopy following endoscopic resection of LLSTs not only to examine resection sites for residual polyps but also to look for missed synchronous lesions.Figure 1.: Characteristics of Synchronous Lesions (n=333). A. Size of Synchronous Lesion B. Location of Synchronous Lesions C. Histology of Synchronous Lesions. Table 1. - Factors Associated with Synchronous Lesions by Multiple Logistic Regression Analysis Odds ratio (95% confidence interval) Standard error Z-value P-value Age 1.04 (1.014-1.071) 0.015 2.99 0.003* Gender 0.86 (0.479-1.535) 0.255 -0.52 0.604 Procedure Time 1.00 (0.977-1.007) 0.255 0.70 0.484 Bowel Cleanliness 0.84 (0.470-1.508) 0.250 -0.58 0.564 Size of index lesion 0.98 (0.959-1.00) 0.013 -1.31 0.191 Location of index lesion 0.96 (0.564-1.627) 0.259 -0.16 0.875 Histology of index lesion 0.62 (0.318-1.20) 0.210 -1.41 0.157 Residual disease 1.48 (0.522-4.20) 0.787 0.74 0.461