Supplementary Material for: Consecutive Uncontrolled Gastrointestinal Immune-Related Adverse Events Induced by Pembrolizumab in a Patient with Lung Adenocarcinoma: A case report

Introduction: Immune-checkpoint inhibitors, such as pembrolizumab, have been used for non-small cell lung cancer treatment but are often associated with immune-related adverse events (ir-AEs). Case presentation: A 71-year-old female, who was diagnosed with lung adenocarcinoma (cT3N0M1c; BRN, cStage IVB [UICC-8th edition]) and was treated with pembrolizumab monotherapy, achieving a partial response. After five cycles, she developed anorexia and abdominal pain, and upper gastrointestinal endoscopy revealed hemorrhagic gastritis because of ir-AEs. Systemic steroids improved the gastritis, and pembrolizumab was re-administered. However, after re-treatment, she developed interstitial lung disease, enteritis, and recurrent gastritis, all of which were ir-AEs. Despite high-dose steroids and infliximab addition, the ir-AEs remained uncontrolled, and the patient eventually died. Conclusion: Caution is essential when re-administering immune-checkpoint inhibitors to patients with prior ir-AEs, although upper gastrointestinal ir-AEs are usually manageable.