EP783 - Bowel Obstruction or Perforation in Patients Undergoing Neoadyubant Inmunotherapy for Mismatch Repair Deficient Colon Cancer

Monday, May 12, 2025

1:31 PM – 1:36 PM PT

Author(s)

FL

Florencia Lucero Serrano, n/a

Colorectal Surgery Department.
Instituto Nacional de Ciencias Médicas y Nutrición "Salvador Zubiran"
Ciudad de México, Distrito Federal, Mexico

Disclosure information not submitted.

Senior Author(s)

OS

Oscar Santes, MD, MRCS (Ed), FEBS (Coloproctology) (he/him/his)

Consultant Colorectal Surgeon
Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran
Mexico City, Distrito Federal, Mexico

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

ePoster Presenter(s)

Claudia Alejandra Anton Velez, MD (she/her/hers)

Colorectal Surgery Department.
Instituto Nacional de Ciencias Médicas y Nutrición "Salvador Zubiran"
Guatemala, Guatemala, Guatemala

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

Author(s)

NS

Noel Salgado-Nesme, n/a

Colorectal Surgery Department.
Instituto Nacional de Ciencias Medicas Y Nutrición Salvador Zubirán
Ciudad de México, Distrito Federal, Mexico

Disclosure information not submitted.

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

Oscar Santes, MD, MRCS (Ed), FEBS (Coloproctology): This individual has no financial relationships with ineligible companies.

Claudia Alejandra Anton Velez, MD: This individual has no financial relationships with ineligible companies.

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Purpose/Background: Neoadjuvant immunotherapy for mismatch repair deficient (dMMR) localized colon cancer achieves an impressive rate of pathologic responses. To assist with safe patient classification and decision-making, it is imperative to identify treatment-related complications resulting from the surgical postponement. Bowel obstruction and perforation are potential negative outcomes due to the tumor site inflammation, necrosis, and fibrosis. To our knowledge, there is only one multicentric case series, analyzing nine patients, that draws attention to bowel obstruction as a developing risk associated with neoadjuvant immunotherapy.

Methods/Interventions: Retrospective case series from 2022 to 2024 at a single center. All patients receiving neoadjuvant immunotherapy for a dMMR primary colonic cancer who experienced intestinal obstruction or perforation were included. Data on patient, tumor characteristics, treatment and outcomes were inspected for potential risk factors.

Results/Outcomes: Four patients were included, three were women (75%) and the median age was 63 years (IQR 18.5). Most often, tumors were found at the colic flexures (75%). All the tumors had an annular shape, three of them (75%) exhibited radiographic stricture that correlated endoscopically with a near-complete luminal stenosis. The predominant neoadjuvant immunotherapy regimen was nivolumab/ipilimumab (75%), with a median of five cycles administered (IQR 3.5). The development of adverse events (obstruction or perforation) that granted surgery occurred at a median time of 182 days (IQR 162.5) after starting immunotherapy. Radiographic response, pathologic staging and tumor regression grade (TRG) are shown in Table 1.

Conclusion/Discussion: Although neoadjuvant immunotherapy for colon cancer may be successful in producing a complete pathological response, patients are at risk of intestinal obstruction or perforation during treatment, which may prompt surgery. Annular-shaped tumors at the colic flexures displaying radiographic or endoscopic narrowing seem to increase the risk of bowel obstruction and perforation. Our results are comparable to those of the multicentric series that Platt JR et al. published.