A population-based analysis on the incidence of metachronous colon cancer after endoscopic resection of advanced adenomas with high-grade dysplasia: does location matter?

Background Advanced adenomas with high-grade dysplasia represent a risk factor for metachronous neoplasia, with guidelines recommending short-interval surveillance. While the worse prognosis of proximal (vs. distal) colon cancers is established, there is paucity of evidence on the impact of laterality on the risk of subsequent neoplasia for these advanced adenomas. Methods Adults with high-grade dysplasia adenomas undergoing polypectomy were identified in the Surveillance, Epidemiology, and End Results database (2000-2019). Cumulative incidence of malignancy was estimated using the Kaplan-Meier method. Fine-Gray models assessed the effect of patient and disease characteristics on colon cancer incidence. Results Of 3,199 patients, 26% had proximal advanced adenomas. Sixty-five cases of metachronous adenocarcinoma were identified after polypectomy of 35 proximal and 30 distal adenomas with high-grade dysplasia. The 10-year cumulative incidence of colon cancer was 2.3%; when stratified by location, it was 4.8% for proximal vs. 1.4% for distal adenomas. Proximal location was significantly associated with increased incidence of metachronous cancer (adjusted HR 3.32, 95% CI 2.05-5.38). Conclusions Proximal location of advanced adenomas with high-grade dysplasia was associated with >3-fold increased incidence of metachronous colon cancer and shorter time to diagnosis. These data suggest laterality should be considered in the treatment and follow-up of these patients.