P4159 - Rare Case of Large Duodenal Ulcer From Immune Checkpoint Inhibitor Therapy

Harshitha Mogallapalli, MD¹, Jennifer Weiss, MD, MS²
1University of Wisconsin Hospitals and Clinics, Madison, WI; 2University of Wisconsin School of Medicine and Public Health, Madison, WI

Introduction: Increased use of immune checkpoint inhibitors (ICIs) to treat solid organ tumors increases the incidence of immune related adverse effects (IrAEs) seen by gastroenterologists. 60-70% of people on ICIs experience side effects with GI toxicity being one of the most common. The most commonly involved GI organs are the colon, liver, and pancreas, with upper GI involvement being rare; 3-5.4% on immunotherapy.

Case Description/

Methods: A 33 year old female with ER/PR(-), HER2+ invasive ductal carcinoma and PMS2-Lynch Syndrome presented with 1 month of dyspepsia while eating. Her treatment course included neoadjuvant chemotherapy with carboplatin, paclitaxel, and pembrolizumab, a left partial mastectomy with no residual carcinoma and subsequent adjuvant chemotherapy with cyclophosphamide, doxorubicin and pembrolizumab. 5 months into her ICI therapy, she developed worsening dyspepsia and epigastric pain. Pancreatitis was ruled out with a normal amylase and lipase. Prior to ICI treatment, any GERD symptoms had been well-controlled with famotidine. Omeprazole was initiated and EGD was initially deferred due to neutropenia.



Unfortunately, symptoms worsened to daily debilitating abdominal pain despite increasing doses of omeprazole and adding sucralfate. Pembrolizumab was held and EGD was obtained once the neutropenia resolved. EGD showed patchy inflammation of the gastric body and a large, non-bleeding, superficial, clean based duodenal ulcer (30mm x 10mm). Biopsies taken in the stomach and duodenum showed active gastritis and duodenitis with erosions and rare crypt epithelial cell apoptosis consistent with ICI gastritis/duodenitis. H. pylori and CMV testing was negative. Omeprazole dose was maximized, sucralfate was continued and she was recommended to discontinue her pembrolizumab treatment to avoid further ICI related complications.

Discussion: Immune checkpoint inhibitor related adverse effects (IrAEs) involving the upper GI tract are rare and lacking in a formal grading system and treatment algorithms, unlike ICI colitis. However, as depicted in this case, they can cause significant distress and possibly lead to severe inflammation and ulcer formation. In order to recognize, diagnose and treat these rare side effects early and effectively there should be strong collaboration between oncologists and gastroenterologists. This case highlights the need for further research into the pathophysiology and guidance for management of ICI induced duodenitis and gastritis as ICI use becomes more common.

Disclosures:
Harshitha Mogallapalli indicated no relevant financial relationships.
Jennifer Weiss: Exact Sciences – Grant/Research Support.

Harshitha Mogallapalli, MD¹, Jennifer Weiss, MD, MS². P4159 - Rare Case of Large Duodenal Ulcer From Immune Checkpoint Inhibitor Therapy, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.