P404 - Proximal Adenomas with High-Grade Dysplasia are Associated with Increased Cumulative Incidence of Post-polypectomy Colon Cancer: A SEER-Medicare Analysis

Tuesday, May 13, 2025

8:30 AM – 8:36 AM PT

Location: Ballroom 6B, Upper Level

Abstract Podium Presenter(s)

Julia Frebault, MD

General Surgery Research Resident
University of Minnesota
Minneapolis, MN, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.

Author(s)

Alexander M. Troester, MD (he/him/his)

General Surgery Resident
University of Minnesota
University of Minnesota
Minneapolis, MN, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
Lauren Weaver, MD

Resident
University of Minnesota
University of Minnesota
Minneapolis, MN, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
IH

Imran Hassan, MD

Attending Surgeon
Mercy Medical Center
Cedar Rapids, Iowa, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.
SM

Sarah Mott, MS

Biostatistician
University of Iowa Holden Comprehensive Cancer Center
Iowa City, Iowa, United States

Disclosure information not submitted.
AS

Aasma Shaukat, MD MPH

Professor
New York University Grossman School of Medicine
scarsdale, New York, United States

Disclosure information not submitted.
SM

Schelomo Marmor, PhD

Associate Professor
University of Minnesota
Minneapolis, Minnesota, United States

Disclosure information not submitted.

Senior Author(s)

PG

Paolo Goffredo, MD (he/him/his)

Assistant Professor
University of Minnesota
Minneapolis, MN, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.

Submitting Author(s)

Julia Frebault, MD

General Surgery Research Resident
University of Minnesota
Minneapolis, MN, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no financial relationships with ineligible companies.

All of the relevant financial relationships listed below have been mitigated.

Julia Frebault, MD: This individual has no financial relationships with ineligible companies.

Alexander M. Troester, MD: This individual has no financial relationships with ineligible companies.

Lauren Weaver, MD: This individual has no financial relationships with ineligible companies.

Imran Hassan, MD: This individual has no financial relationships with ineligible companies.

Paolo Goffredo, MD: This individual has no financial relationships with ineligible companies.

Image or Table (Do Not add text here):

Purpose/Background: Carcinomas in situ (Tis), also defined as an adenomas with high grade dysplasia (HGD), are categorized among the advanced adenomas for which current guidelines recommend a short interval post-polypectomy surveillance of 3 years due to the increased risk for metachronous neoplasia. Over the past decade, proximal colon cancers have been shown to have worse prognosis compared to distal tumors. However, there is a scarcity of data on the impact of location of HGD adenoma on the subsequent risk of developing colon cancer. We hypothesized that patients with proximal HGD adenomas would have a higher incidence of metachronous neoplasia after undergoing endoscopic polypectomy.

Methods/Interventions: Adults aged ≥65 years with history of HGD adenoma undergoing polypectomy with at least one surveillance procedure after diagnosis were identified in the Surveillance, Epidemiology, and End Results-Medicare-linked database (2006-2019). Those with a malignant diagnosis within 6 months of HGD adenoma diagnosis were excluded. Time to metachronous malignancy was calculated from HGD adenoma diagnosis to diagnosis of invasive colon cancer. Cox regression was used to assess the effect of adenoma location on metachronous malignancy. Survival was assessed with a Kaplan-Meier model.

Results/Outcomes: A total of 523 patients were identified: 41% had proximal adenomas with HGD. There were no differences in demographics between patients with proximal vs distal lesions (56% male, 82% Caucasian, median age =73 years). While the overall 10-year cumulative incidence of subsequent colon cancer was 17%; when stratified by location, it was 33% for proximal compared to 8% for distal HGD adenomas (Figure 1). Median time to diagnosis of metachronous colon cancer was 2.8 years for proximal vs 4.1 years for distal HGD adenomas. On multivariable analysis, proximal location was significantly associated with increased incidence of metachronous cancer (adjusted hazard ratio: 4.19; 95% CI:1.90-9.26) after adjusting for age and sex. Patients with proximal HGD adenomas had worse five-year overall survival after metachronous cancer diagnosis compared with distal lesions (57% vs 38%).

Conclusion/Discussion: In this large population-based cohort, proximal location of HGD adenomas was associated with a four-fold increase in incidence of metachronous colon cancer. Additionally, proximal lesions had a shorter time to diagnosis and worse overall survival. These data suggest that location of adenomas with HGD within the colon should be taken into consideration when determining clinical management of these lesions.