eP170 - A Population-Level Validation of the New 9th Edition American Joint Commission on Cancer Staging System for Anal Squamous Cell Carcinoma

ePoster Presenter(s)

• 

  Aos Karim, MD

  Colon and Rectal Surgery Fellow
  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.

Author(s)

• 

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

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

  All relevant financial disclosures have been managed and will be listed below.
  This individual has no financial relationships with ineligible companies.
• SM

  Sarah Mott, MS

  Biostatistician
  University of Iowa
  Iowa City, Iowa, United States

  Disclosure information not submitted.
• EA

  Elliot G. Arsoniadis, MD, PhD

  Assistant Professor of Surgery
  University of Minnesota Department of Surgery
  Minneapolis, Minnesota, United States

  Disclosure information not submitted.
• 

  Christine C. Jensen, MD MPH

  Adjunct Associate Professor
  University of Minnesota
  University of Minnesota
  Coon Rapids, MN, United States

  All relevant financial disclosures have been managed and will be listed below.
  This individual has no financial relationships with ineligible companies.
• IH

  Imran Hassan, MD

  Adjunct Clinical Professor
  University of Iowa
  Cedar Rapids, Iowa, United States

  All relevant financial disclosures have been managed and will be listed below.
  This individual has no financial relationships with ineligible companies.
• PK

  Pridvi Kandagatla, MD

  Colorectal Surgeon
  Colon and Rectal Surgery Associates
  St. Paul, Minnesota, United States

  Disclosure information not submitted.

Senior Author(s)

• PG

  Paolo Goffredo, MD

  Assistant Professor
  University of Minnesota
  Minneapolis, Minnesota, United States

  Disclosure information not submitted.

Purpose/Background: In January 2023, the American Joint Commission on Cancer (AJCC) revised the staging system for anal squamous cell carcinoma (ASCC), downstaging selected node positive patients and upstaging some with larger tumors. This change was based solely on a National Cancer Database study demonstrating paradoxical better overall survival (OS) rates for patients with Stage IIIA (73.7%) compared to Stage IIB (63.5%). The aim of this study was to validate this updated staging system using a population-based database as well as evaluate its effects on cancer specific survival (CSS) prognostication.Methods/Interventions: The Surveillance, Epidemiology, and End Results database (SEER) was analyzed to identify adult ASCC patients with only one lifetime cancer diagnosis and available survival data. After meeting inclusion criteria, patients were staged according to the AJCC 8th and 9th edition staging system (Table 1). Those diagnosed prior to 2018 were excluded due to differences in definitions of what constitutes regional versus metastatic nodal disease in the AJCC 7th edition guidelines. Survival probabilities were estimated using the Kaplan-Meier method. Multivariable Cox regression models were utilized to estimate the effect of stage on OS and CSS after adjusting for confounders (e.g. age, sex, race, primary site, and treatment).Results/Outcomes: A total of 2,117 patients with ASCC were identified and staged based on the two AJCC classifications. Most were younger than 70 years old (74%), were female (68%), Caucasian (88%), and all were diagnosed with ASCC between 2018 and 2020. Median follow-up time was 15 months. OS and CSS rates are reported in Table 1. At 24 months, we noted a similar paradoxical OS and CSS between Stage IIB and Stage IIIA disease using the 8th edition staging system (Table 1). Conversely, when patients were staged using the updated 9th edition classification, there was now an incremental decrease in OS and CSS rates with increasing stage. These results were confirmed in a separate multivariable analysis adjusting for confounders showing again a higher hazard ratio (HR) relative to Stage I for OS (Stage IIB: HR 6.23 vs Stage IIIA: HR 5.48) and CSS (Stage IIB: HR 7.67 vs Stage IIIA: HR 6.05) in Stage IIB compared to Stage IIIA disease using the 8th edition staging system, and a logically progressive increase in HRs using the 9th edition staging system (OS: Stage IIB: HR 5.42 vs Stage IIIA: HR 7.69; CSS: Stage IIB: HR 5.92 vs Stage IIIA: HR 10.61).Conclusion/

Discussion: In this large, population-based cohort of patients with ASCC, the hierarchical increase of the OS and CSS HRs across all stages validated the updated edition (9th) of the AJCC staging system. Although this change does not have significant implication on the management of ASCC, it could provide better prognostication for these patients based on clinical staging.Table 1. Comparison of 24 Month Overall and Cancer Specific Survival and Hazard Ratio Per Stage Between the 8th and the 9th Edition of the AJCC Staging System for ASCC