eP180 - Discordinant Clinical Responses to Immunotherapy in Patient with Synchronous dMMR Colon and Rectal Adenocarcinomas

Sunday, June 2, 2024

8:00 AM – 8:05 AM ET, USA

Location: Baltimore Convention Center, Room 318-320

Senior Author(s)

ST

Steven Tsoraides, MD, MPH

Attending Surgeon
University of Illinois College of Medicine at Peoria, Springfield Clinic
Peoria, Illinois, United States

Disclosure information not submitted.

ePoster Presenter(s)

Frank A. DiSilvio, Jr., MD

Resident
University of Illinois College of Medicine at Peoria
University of Illinois College of Medicine at Peoria
Peoria, IL, United States

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

Author(s)

Ayo N. Gazal, MD (she/her/hers)

General Surgery Resident
University of Illinois College of Medicine at Peoria
University of Illinois College of Medicine - Peoria
Peoria, IL, United States

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

General Surgery Resident
University of Illinois College of Medicine at Peoria
University of Illinois College of Medicine at Peoria
Peoria, IL, United States

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

Madhuri Bajaj, MD

Associate Professor
University of Illinois College of Medicine at Peoria
Peoria, Illinois, United States

Disclosure information not submitted.

Purpose/Background: Evolving data reveals encouraging results in the use of checkpoint inhibitor immunotherapy for colorectal cancers with metastatic disease and rectal adenocarcinoma treated with curative intent. Series of complete clinical response of rectal cancers to immunotherapy have altered guidelines for care. Here is an index case of synchronous colon and rectal adenocarcinoma with incomplete clinical response of the rectal primary and complete clinical response of the colon primary.Methods/Interventions: Retrospective medical record review of an individual case treated at a collaborative multidisciplinary cancer center.Results/Outcomes: 42 year old male diagnosed with synchronous MSH-6 deficient ascending colon and rectal adenocarcinomas after experiencing abdominal pain and bleeding. Subsequent germline testing confirmed Lynch Syndrome. Given recent reports of immunotherapy yielding complete response for rectal adenocarcinoma, and after appropriate consent, the patient was treated with 6 months of dostarlimab. Endoscopy at the end of treatment revealed complete response of his ascending colon cancer and incomplete response of his rectal adenocarcinoma. Based on this, he completed concurrent chemoradiation followed by systemic chemotherapy based on Total Neoadjuvant Therapy protocols for rectal cancer. Resection options include total proctocolectomy with end ileostomy vs. APR given the complete response, although this would not be evidence-based at this time.Conclusion/

Discussion: While encouraging data have been reported on the use of immunotherapy for isolated dMMR rectal adenocarcinoma, patients with synchronous dMMR abdominal colon adenocarcinoma may represent a group where immunotherapy may not be expected to yield a complete response of the rectal primary. Unexpectedly, there was a discordant response and the colon cancer did reveal a complete clinical response, resulting in a treatment decision dilemma for the care team.