EP971 - From Prophesy to Pathology: Can Surgeons Accurately Predict Clinical Complete Response Following TNT in Primary Rectal Cancer?

Tuesday, May 13, 2025

8:16 AM – 8:21 AM PT

ePoster Presenter(s)

James G. Connolly, MD

Fellow
Lahey Hospital and Medical Center
New York, NY, United States

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

Author(s)

Racquel S. Gaetani, MD (she/her/hers)

General Surgery Resident/Colorectal Research Fellow
LAHEY HOSPITAL AND MEDICAL CENTER
Lahey Hospital and Medical Center
Burlington, MA, United States

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

Jeremy R. Wortman, MD

Attending
Lahey Hospital and Medical Center
Burlington, Massachusetts, United States

Disclosure information not submitted.
JA

Jalil Afnan, MD

Senior Staff, Department of Radiology
Lahey Hospital and Medical Center
Burlington, Massachusetts, United States

Disclosure information not submitted.
EK

Ethan Krug, MD

Resident
Lahey Hospital and Medical Center
Burlington, Massachusetts, United States

Disclosure information not submitted.
Jonathan T. Bliggenstorfer, MD

Fellow in Colon and Rectal Surgery
Lahey Clinic
Burlington, MA, United States

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

Cody W. Munroe, MS

Coordinator
Lahey Hospital and Medical Center
Burlington, Massachusetts, United States

Disclosure information not submitted.
David A. Kleiman, MD, MSc, FACS, FASCRS (he/him/his)

Staff Surgeon, Division of Colon & Rectal Surgery
Lahey Hospital & Medical Center
Melrose, Massachusetts, United States

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This individual has no relevant relationships with ineligible companies.
JS

Julia T. Saraidaridis, MD, MMSc

Assistant Professor of Surgery, Tufts University School of Medicine
Lahey Clinic
Burlington, Massachusetts, United States

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This individual has no financial relationships with ineligible companies.
AK

Angela H. Kuhnen, MD, MPH (she/her/hers)

Attending
Lahey Hospital and Medical Center
Tufts University School of Medicine
Burlington, Massachusetts, United States

All of the relevant financial relationships listed below have been mitigated.
This individual has no relevant relationships with ineligible companies.
Peter W. Marcello, MD (he/him/his)

Attending
Lahey Hospital and Medical Center
Burlington, Massachusetts, United States

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This individual has no relevant relationships with ineligible companies.

Senior Author(s)

Jonathan S. Abelson, MD MS (he/him/his)

Staff Surgeon
Lahey Hospital and Medical Center
Tufts Medical Center
Arlington, Massachusetts, 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.

James G. Connolly, MD: This individual has no financial relationships with ineligible companies.

Racquel S. Gaetani, MD: This individual has no financial relationships with ineligible companies.

Jonathan T. Bliggenstorfer, MD: This individual has no financial relationships with ineligible companies.

David A. Kleiman, MD, MSc, FACS, FASCRS: This individual has no relevant relationships with ineligible companies.

Julia T. Saraidaridis, MD, MMSc: This individual has no financial relationships with ineligible companies.

Angela H. Kuhnen, MD, MPH: This individual has no relevant relationships with ineligible companies.

Peter W. Marcello, MD: This individual has no relevant relationships with ineligible companies.

Jonathan S. Abelson, MD MS: This individual has no financial relationships with ineligible companies.

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Purpose/Background: The ability to accurately predict tumor treatment response after total neoadjuvant therapy (TNT) is a critical step towards safely offering watch and wait strategies. Practitioners use a multimodal approach to determine clinical response which includes digital rectal exam, endoscopy, and pelvic MRI. It is unknown how well surgeons can predict clinical complete response (cCR) after TNT. We aimed to determine surgeons’ ability to predict treatment response by comparing clinical and pathologic response rates for patients with primary rectal adenocarcinoma who underwent TNT followed by curative intent surgery.

Methods/Interventions: We performed a retrospective review of a prospectively maintained database of all patients with locally advanced or oligometastatic primary rectal adenocarcinoma from a single institution from 8/2021 to 5/2024. Patients received TNT with either induction or consolidation chemotherapy. Surgeons’ self-reported clinical tumor response to therapy was recorded based on changes in tumor characteristics assessed via pre- and post-treatment digital rectal exam (DRE), endoscopy and T2- and DW-pelvic MRI. All patients subsequently underwent a total mesorectal excision (TME) with curative intent and evaluation of pathologic treatment response. The primary outcome was concordance between the surgeon predicted clinical response with pathologic response.

Results/Outcomes: There were 46 patients included for analysis. Almost all patients (96%) had locally advanced rectal cancer, thirty-one patients (67%) had clinical node-positive disease, and two patients (4%) had oligometastatic metastatic disease to the liver. Twenty-six patients (57%) had a palpable mass on pre-treatment exam. The median time from completion of TNT to surgery was 10 weeks (IQR, 8-14 weeks). Following TNT, 25 patients (54%) had a clinical incomplete response, 11 patients (24%) had a near-complete response, and 10 patients (22%) had a complete response with 9 of those patients having a local regrowth without distant metastasis. Of the 34 clinical incomplete response and regrowth patients, six patients (18%) had pCR. For the 11 near-complete response patients, two (18%) patients had a pCR. A biopsy of the tumor was obtained in 1 near-complete response case to confirm diagnosis prior to surgery. There was an 87% concordance rate between surgeons’ predicted clinical and pathologic response. When broken down by assessment tool, endoscopy and MRI had 89% and 73% concordance rates with pathologic response, respectively.

Conclusion/Discussion: We found that surgeons are well equipped to predict pathologic response to TNT with the aid of physical exam, endoscopy and pelvic MRI reaching concordance rates approaching 90%. For those discordant cases, surgeons underestimated tumor treatment response and a fraction of patients with pCR underwent TME because of presumed clinical incomplete response.