Immune-Related Esophagitis and Durable Response to Second-Line Treatment With Nivolumab in Stage IV Squamous Cell Esophageal Carcinoma.

Immune checkpoint inhibitors such as nivolumab have transformed the management of advanced cancers but may lead to immune-related adverse events, including rare toxicities affecting the upper gastrointestinal tract. Isolated immune-mediated esophagitis is uncommon, particularly in esophageal squamous cell carcinoma, and its clinical implications remain poorly characterized. We report the case of a 78-year-old male with advanced esophageal squamous cell carcinoma who developed epigastric pain, dysphagia, and weight loss seven months after initiating nivolumab therapy. Endoscopy revealed ulcerative esophagitis, and histology confirmed chronic inflammation, with infectious etiologies ruled out. Nivolumab was discontinued, and the patient was managed with proton pump inhibitors and high-dose corticosteroids, resulting in significant symptom improvement. At the time of immunotherapy discontinuation, the patient had achieved a radiologic partial response. Remarkably, during follow-up without further oncologic therapy, his disease continued to regress, culminating in a complete response that has been sustained for twenty-one months. This case is notable for the unique combination of advanced esophageal squamous cell carcinoma, isolated nivolumab-induced esophagitis, and a durable tumor response sustained long after immunotherapy discontinuation, underscoring the importance of recognizing immune-mediated toxicities and their potential association with robust antitumor activity.