S4381 Immune Checkpoint Inhibitor-Induced Esophagitis Mimicking Reflux and Infectious Etiologies: A Rare but Emerging Gastrointestinal Immune-Related Adverse Effect

Introduction: Immune checkpoint inhibitor (ICI) use continues to increase as they have become a cornerstone in the treatment of numerous cancers. ICI-induced esophagitis is a rare but significant immune-related adverse event associated with the use of ICIs such as anti-PD-1, anti-PD-L1, and anti-CTLA-4 therapies. Case Description/Methods: We present a case of a 79-year-old woman with relevant history of high-grade, metastatic neuroendocrine bladder cancer on pembrolizumab who presented to the hospital 10 months after ICI initiation with odynophagia and dysphagia of 2-month duration. Their symptoms had been previously evaluated in an emergency department and in two urgent care visits. Initially prescribed viscous lidocaine and prednisone with brief symptomatic improvement, they experienced symptom recurrence after completion of corticosteroids. Then, their symptoms persisted despite an extended course of fluconazole prescribed to empirically treat suspected esophageal candidiasis. Four weeks after hospital discharge, the patient underwent an outpatient esophagogastroduodenoscopy (EGD) that found many linear ulcerations ranging from 2-10 cm throughout the entire esophagus. Subsequent biopsies revealed lymphocytic inflammation of squamous epithelium with apoptotic bodies consistent with ICI-induced esophagitis. Pembrolizumab was held for 4 weeks while they received an oral budesonide taper and esomeprazole. Eight weeks after initiation of glucocorticoid and proton-pump inhibitor, the patient returned for outpatient follow-up and endorsed complete resolution of odynophagia and dysphagia. An EGD was repeated, demonstrating resolution of linear esophageal ulcerations, normal mucosa of the upper-third esophagus, textured mucosal changes of the middle-third of esophagus, and non-obstructing stenosis at the same level. Biopsies from the post-treatment EGD demonstrated improvement in the number of dyskeratotic keratinocytes and dramatic reduction in intraepithelial lymphocytes. Discussion: Although rare, it is increasingly important that physicians be able to recognize and treat ICI-induced esophagitis. Clinically, the presentation of this immune-related adverse event may mimic other, more common, forms of esophagitis. However, it has a distinct histopathological appearance on biopsy that necessitates EGD to confirm the diagnosis.