Abstract
BACKGROUND: Immune checkpoint inhibitors might cause immune-related adverse events that are still largely unknown. CASE PRESENTATION: An 80-year-old Asian female was diagnosed with cervical lymph node metastasis from lip cancer (cT1N0M0) and underwent right cervical neck dissection. Subsequently, she developed right cervical lymph node relapse and lung metastasis. The patient was deemed eligible for pembrolizumab owing to unresectable neck recurrence and pulmonary metastasis. The Combined Positive Score of the submandibular lymph nodes was 100. Pembrolizumab monotherapy was initiated, and complete remission was achieved. She developed diabetic ketoacidosis in the eighth month and was diagnosed with fulminant type 1 diabetes mellitus. Insulin induction was performed. The patient developed adrenal insufficiency after 10 months. These were immune-related adverse events, caused by pembrolizumab. The patient has remained in complete remission, and pembrolizumab therapy was continued. CONCLUSIONS: The study presents the first reported case of type 1 diabetes in a patient with head and neck squamous cell carcinoma treated with pembrolizumab monotherapy, in Japan. Efficient interdepartmental collaboration will promote the management of severe immune-related adverse events and improve the quality of life of patients.