A Case of Nonsmall-Cell Lung Cancer with Anaphylaxis after 41 Courses of Pembrolizumab along with Adrenal Insufficiency as an Immune-Related Adverse Event

In this report, we present a case of nonsmall-cell lung cancer with anaphylaxis after 41 courses of pembrolizumab along with adrenal insufficiency as an immune-related adverse event (irAE). A 73-year-old man with no allergic disease started pembrolizumab for postoperative recurrence of lung cancer. After four courses, tumor shrinkage was observed and maintained thereafter. After the 39th course, his serum sodium level and random serum cortisol level decreased. Adrenal insufficiency was considered; however, the patient was asymptomatic. Furthermore, his serum sodium level improved spontaneously; therefore, he was followed up. At the end of the 40th course, rhinorrhea and pharyngeal discomfort were noted; however, they were mild and resolved spontaneously. Immediately after administration of the 41st course, he developed pembrolizumab-induced anaphylaxis with percutaneous oxygen saturation decreased. The symptoms quickly improved after intramuscular adrenaline were administered and did not recur. Three months after discharge, the patient was urgently examined for vomiting and anorexia. His serum sodium levels decreased to 119 mEq/L, and an adrenocorticotropic hormone stimulation test was performed. It showed a low response, and the patient was diagnosed with secondary adrenal insufficiency as an irAE of pembrolizumab and treated with hydrocortisone, which quickly improved his serum sodium levels and symptoms. When adrenal insufficiency develops due to irAEs, patients may be susceptible to allergic reactions.