Atezolizumab-Induced Type 1 Diabetic Ketoacidosis in a Patient With Small Cell Lung Cancer and Pre-existing Type 2 Diabetes Mellitus.

In this report, we present a case of a 70-year-old male with small cell lung cancer (SCLC) and pre-existing type 2 diabetes mellitus (T2DM) who developed type 1 diabetic ketoacidosis (DKA) following treatment with atezolizumab plus chemotherapy. Despite well-controlled T2DM with oral hypoglycemic agents, the initiation of immune checkpoint inhibitors (ICIs) led to rapid deterioration into insulin-dependent status due to ICI-induced type 1 diabetes mellitus (T1DM). Vigilant monitoring for hyperglycemia and timely intervention is crucial during ICI therapy, considering the potentially life-threatening complications. Although the patient achieved extended progression-free survival (PFS) post-treatment, re-administration of atezolizumab resulted in a bullous pemphigoid-like rash, necessitating discontinuation of the drug and corticosteroid treatment. The impact of recurring immune-related adverse events (irAEs) on treatment efficacy warrants further investigation.