EP365 - Quality of total mesorectal excision after Short- vs. Long-course Radiation: Evaluation of a Contemporary National Cohort

ePoster Presenter(s)

• 

  Keegan Guidolin, MD, PhD

  Clinical Fellow, Colon & Rectal Surgery
  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)

• 

  Rachel Jensen, MD MHPE

  Colon and Rectal Surgery Fellow
  University of Minnesota
  University of Minnesota
  Minneapolis, MN, United States

  Disclosure information not submitted.
• 

  Julia Frebault, MD (she/her/hers)

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

  Disclosure information not submitted.
• SM

  Sarah Mott, MS

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

  Disclosure information not submitted.
• DD

  Dayssy Diaz, M.D, MS

  Professor
  University of Minnesota
  Minneapolis, Minnesota, United States

  Disclosure information not submitted.
• CT

  Catherine Tran, MD

  Colon & Rectal Surgeon
  Colon & Rectal Surgery Associates
  Minneapolis, Minnesota, United States

  Disclosure information not submitted.
• IH

  Imran Hassan, MD

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

  Disclosure information not submitted.

Senior Author(s)

• 

  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.

Purpose/Background: Pathologic grading of the total mesorectal excision (TME) specimen has become a key quality metric of rectal cancer care. Recent literature suggested that short-course neoadjuvant radiation therapy (SC-NRT) is associated with poorer quality TME specimens compared to long-course (LC) NRT; however, there is a scarcity of data at a national level. This study aimed to investigate the impact of SC- vs LC-NRT on surgical quality, as well as factors associated with TME completeness in a contemporary, US-based series of patients who received total neoadjuvant therapy (TNT).

Methods/Interventions: Adults with clinical stage II-III rectal adenocarcinoma diagnosed in 2022 and managed with TNT and proctectomy were identified in the National Cancer Database (NCDB). The SC-NRT regimen received was 25 Gy over 5-8 days, while the LC-NRT regiment was 45-70 Gy over 33-50 days. Multinomial logistic regression assessed associations between patient, clinical, and treatment characteristics and completeness of TME on macroscopic pathologic assessment. This is a novel variable collected only in the latest year of NCDB release; therefore, survival analyses could not be performed.

Results/Outcomes: Of 1,345 patients (63% male, 86% white, 85% < 70 years old), 1,118 (83%) received LC-NRT and 227 (17%) SC-NRT. Most patients underwent low anterior resection (LAR; 74%) and a robotic procedure (64%). Univariable analysis identified several factors associated with incomplete TME, including lower income, undergoing surgery at a non-academic center, undergoing an abdominoperineal resection (APR, versus LAR), positive resection margins, larger tumor size, elevated carcinoembryonic antigen level, and greater duration of time between the end of radiation and the date of surgery. On multivariable analysis, operation performed (APR versus LAR), positive surgical margins, and increased time between the end of NRT and surgery were associated with an elevated risk of incomplete compared to complete TME (Table 1). Increased time from NRT to surgery was linearly associated with increased odds of incomplete TME; however, the NRT protocol (LC- vs SC-NRT) was not significantly associated with completeness of TME.

Conclusion/Discussion: In this national cohort of patients with stage II-III rectal cancer undergoing proctectomy following TNT, less than one in five patients underwent SC-NRT, which was not associated with higher odds of breach of the mesorectum. Notwithstanding the limitations of this database, which excludes rates of complete clinical response, our data also suggest that appropriate timing of surgery after radiation significantly impacts completeness of the TME, creating a potential challenge in balancing surgical approach with safe organ preservation strategies.

Table 1. Multivariable analysis of clinicopathologic factors associated with total mesorectal excision (TME) quality.
TME = total mesorectal excision, OR = odds ratio, CI = confidence interval, APR = abdominoperineal resection, LAR = low anterior resection, CRM = circumferential radial margins, RT = radiation therapy