Endocrinologist‐Led Management of Endocrine Immune‐Related Adverse Events: Real‐World Evidence Supporting the Japan Endocrine Society Guidelines

This retrospective observational study assessed the real-world management of endocrine immune-related adverse events (irAEs) in 84 patients treated with immune checkpoint inhibitors (ICIs) at a single center in Japan. Care was provided by endocrinologists and evaluated for consistency with the Japan Endocrine Society (JES) guidelines. Thyroid dysfunction (64.3%) and adrenal insufficiency (42.9%) were the most frequent irAEs, followed by hypophysitis and insulin-dependent diabetes mellitus (each 8.3%). Management generally conformed to JES recommendations, including levothyroxine and hydrocortisone replacement at guideline-recommended doses. More than 80% of patients received maintenance therapy as recommended in the JES guidelines. In some cases, higher hydrocortisone doses were administered based on clinical judgment, particularly in patients with malignancy-related poor general condition. No hospitalizations occurred for thyroid dysfunction, whereas four patients were admitted for adrenal insufficiency-related sick day management. For the treatment of hypophysitis, continuous hydrocortisone replacement therapy was commonly administered. All cases of ICI-induced diabetes presented with severe hyperglycemia, highlighting the importance of early recognition. Survival analysis indicated a trend toward improved prognosis in patients with renal cell carcinoma who developed endocrine irAEs. Notably, the occurrence of endocrine irAE did not directly necessitate switching or discontinuation of ICI therapy. Although limited by its single-center design and the possibility of underreporting, this study provides valuable clinical insights into endocrine irAE management and supports the feasibility of JES guidelines. These findings underscore the importance of specialized endocrine care and guideline-based management in optimizing safety and long-term outcomes in ICI-treated cancer patients, particularly in settings with limited endocrinology resources.