Recovery from insulin dependence in immune checkpoint inhibitor‐associated diabetes mellitus: A case report

Immune checkpoint inhibitor‐associated diabetes mellitus (ICI‐DM) is a rare immune‐related adverse event and is usually considered permanent. Here, we report the first case of a 54‐year‐old man with ICI‐DM who recovered from insulin dependence. He was diagnosed with lung cancer and started pembrolizumab therapy. After seven cycles, he developed ICI‐associated secondary adrenal insufficiency and started hydrocortisone supplementation. Subsequently, he complained of fatigue, and blood examinations showed hyperglycemia with ketosis. A glucagon challenge test indicated insulin dependence. He was diagnosed with ICI‐DM and insulin therapy was initiated. Pembrolizumab therapy was discontinued due to concomitant ICI‐associated hepatitis. Six months later, a glucagon challenge test result showed an improvement in insulin secretion, and insulin therapy was discontinued. The lung cancer lesions continued to shrink. Even if ICI‐DM develops, it might be possible to control the underlying cancer while avoiding lifelong insulin therapy through early discontinuation of ICI.