The Prognostic Significance of Laterality in Endoscopically Resected Colonic Adenomas With High-Grade Dysplasia

Background and Aims: Advanced adenomas (AAs) with high-grade dysplasia (HGD) represent risk factors for metachronous neoplasia, for which guidelines recommend short-interval endoscopic surveillance. Although worse survival of proximal colon cancers has been established, the prognostic impact of laterality for AAs with HGD remains unknown. We hypothesized that proximal HGD would have a worse prognosis than distal lesions. Methods: In this retrospective cohort study, adults with HGD managed with endoscopic polypectomy were identified in the National Cancer Database from 2004-2017. Survival probabilities were estimated and plotted using the Kaplan-Meier method. Cox regression models were used to assess the effect of adenoma laterality on overall survival (OS) while adjusting for patient and disease characteristics. One sample log-rank test was employed to compare the survival of patients with that of the US population. Results: Of 3953 patients identified in the database, 29% had proximal lesions, which were more common in elderly, Black, publicly insured, and comorbid patients. Unadjusted 5- and 10-year OS was 81% and 67% for proximal vs 89% and 78% for distal HGD (P < 0.01). In multivariable analysis, proximal location did not demonstrate significantly worse OS (hazard ratio 1.09, 95% confidence interval [CI] 0.92-1.29). When compared with the age- and sex-matched US population, patients with HGD had significantly increased mortality (standardized mortality ratio 1.54, 95% CI 1.42-1.68), which was more pronounced for right-sided AAs. Conclusion: Patients with HGD, particularly those with proximal lesions, had lower OS than the US population. Although proximal location was not independently associated with worse survival, OS may not represent the optimal endpoint for AAs given the low cancer incidence and effective treatment for early-stage tumors. Future research should focus on the risk of metachronous neoplasia to determine adequate surveillance protocols.