QS136 - Organ Preservation after Short-Course Radiation: Is it Comparable to Long-Course?

Sunday, May 11, 2025

4:22 PM – 4:25 PM PT

Location: Room 9, Upper Level

Quick Shot Presenter(s)

Ahmed A. Eltahir, MD MPHS

General Surgery Resident
Washington University School of Medicine
Washington University in St. Louis
St. Louis, MO, United States

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

Author(s)

Oluseye Oduyale, MD MPHS

General Surgery Resident
Washington University School of Medicine
Washington University School of Medicine in St. Louis
St. Louis, Missouri, United States

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

Catherine Zivanov, MD MPHS

General Surgery Resident
Washington University School of Medicine
St. Louis, Missouri, United States

Disclosure information not submitted.
NK

Nathan S. Kau, n/a

Medical Student
Washington University School of Medicine in St. Louis
St. Louis, Missouri, United States

Disclosure information not submitted.
Jared T. Yee

Research Coordinator
Washington University in St. Louis School of Medicine
San Francisco, CA, United States

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

Daniel Hong, MD

Resident
Washington University
St. Louis, Missouri, United States

Disclosure information not submitted.
MI

Michael D. Iglesia, MD, PhD

Instructor in Medicine
Washington University in St. Louis
St. Louis, Missouri, United States

Disclosure information not submitted.
Hyun Kim, MD

Associate Professor
Washington University School of Medicine
St. Louis, Missouri, United States

Disclosure information not submitted.
Steven Hunt, MD

Professor of Surgery
Washington University School of Medicine
St. Louis, Missouri, United States

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

Professor of Surgery
Washington University
Washington University School of Medicine
St Louis, Missouri, United States

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

Senior Author(s)

WC

William C. Chapman, Jr., MD

Assistant Professor
Washington University School of Medicine
St. Louis, Missouri, 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.

Ahmed A. Eltahir, MD MPHS: This individual has no financial relationships with ineligible companies.

Oluseye Oduyale, MD MPHS: This individual has no financial relationships with ineligible companies.

Jared T. Yee: This individual has no financial relationships with ineligible companies.

Steven Hunt, MD: This individual has no financial relationships with ineligible companies.

Matthew Mutch, MD: This individual has no financial relationships with ineligible companies.

William C. Chapman, MD, Jr.: This individual has no financial relationships with ineligible companies.

Image or Table (Do Not add text here):

Purpose/Background: Total neoadjuvant therapy, consisting of long-course radiation and chemotherapy followed by total mesorectal excision (TME), has gained wide acceptance in the treatment of locally advanced rectal cancer in North America. Utilization of short-course radiotherapy, however, has been controversial, particularly within the emerging treatment paradigm of nonoperative management (NOM). Given the paucity of literature on organ preservation outcomes following total neoadjuvant therapy with short-course radiation, we aimed to characterize the efficacy of NOM in patients who achieved a clinical complete response (cCR) after receiving short-course radiation and chemotherapy. We hypothesized that outcomes after short-course radiation would be comparable to long-course standards.

Methods/Interventions: We performed a retrospective cohort analysis of a prospectively maintained database of patients with rectal cancer at a single tertiary academic center. We identified adult patients with rectal cancer initially seen from January 2015 to December 2023 and underwent short-course radiation and chemotherapy. Patients were evaluated for cCR by digital rectal exam, endoscopy, and MRI. Patients who achieved cCR or near cCR and pursued NOM were included in the analysis. Outcomes were local regrowth-free survival and TME-free survival. Time zero was defined as the clinical response evaluation after neoadjuvant treatment. Kaplan-Meier analysis was used to estimate survival outcomes. All statistical analyses were conducted using R.

Results/Outcomes: We identified 359 patients who underwent short-course radiation followed by chemotherapy, the most common being oxaliplatin with either 5-fluorouracil/leucovorin or capecitabine. Of those, 169 (47.1%) achieved cCR or near cCR. One hundred and sixty-one patients initiated NOM with a median follow-up of 25.7 months (IQR, 14.5-47.6) since the start of NOM surveillance. Median time from date of diagnosis to the start of NOM surveillance was 7.6 months (IQR 6.8-8.8), which included completion of neoadjuvant treatment and restaging exams. Among patients who initiated NOM, median age of diagnosis was 60 years (IQR 52-69), 61.5% were male, 93.2% were white, 59.0% had private insurance, and 83.2% had stage II/III disease. Local regrowth-free survival at one year from NOM initiation was 69.9% (95% CI, 62.8%-77.8%) and at two years was 64.1% (95% CI, 56.6%-72.6%). Of the 51 local regrowths, 86.3% occurred within the first year and all regrowths occurred within two years. Four patients in the cohort developed distant disease in the liver. Three developed liver metastases after developing local regrowth and one developed liver metastasis without prior local regrowth. TME-free survival at one year from NOM initiation was 73.7% (95% CI, 66.8%-81.3%) and at two years was 66.5% (95% CI, 59.1%-74.9%).

Conclusion/Discussion: NOM following the administration of short-course radiation results in efficacious organ-preservation, including local regrowth-free survival and TME-free survival, comparable to NOM following the use of long-course chemoradiation. Although this study is limited by its sample size and retrospective nature, it remains one of the largest cohort analyses to date with a robust follow-up duration. Additional studies are needed to both validate durability of outcomes and identify predictors of local regrowth and poor oncologic outcomes.