8114 The Need For Autoantibody Screening And Diagnostic Criteria For Immune-Checkpoint Inhibitor-Induced Type 1 Diabetes

Abstract Disclosure: A. Gupta: None. H. Sanekommu: None. A.B. Ravin: None. M. Akula: None. J. Cheng: None. Background: Immune-checkpoint inhibitors (ICIs) such as Nivolumab have been extensively studied, especially in relation to their side-effect profiles. Patients on Nivolumab are prone to immune-related adverse events (irAEs) including type 1 diabetes mellitus, thyroiditis, and hypopituitarism. Prior studies have indicated that ICIs can unmask existing diabetic autoimmunities, but currently no specific guidelines exist for autoantibody screening prior to initiating treatment. We report a unique case of a young patient with newly diagnosed immune-checkpoint inhibitor-induced type 1 diabetes (ICI-T1DM) who was found to have mixed autoantibody results. Clinical Case: This is a 31-year-old male who was diagnosed with fibrolamellar hepatocellular carcinoma (pT23N0) and underwent partial hepatic resection later that year. Repeat imaging showed new hepatic lesions, thus Nivolumab was initiated. He received a total of three cycles, after which he presented to the hospital with symptoms of fever and nausea; labs were consistent with diabetic ketoacidosis (DKA) for which he was treated with IV insulin and aggressive hydration with successful resolution. Nivolumab was stopped and the patient was discharged on a basal-bolus insulin regimen. Further outpatient workup was significant for A1c 5.9% (n<5.7%), C-peptide (with glucose 220mg/dL) 0.7 (n=0.8-3.9ng/mL), glutamic acid decarboxylase autoantibody (GAD Ab) 11 (n<5.0U/mL). Insulin antibody and islet cell antibody IgG were negative. Due to the acute onset in the presentation and the recent use of Nivolumab, the patient was diagnosed with ICI-T1DM. He remained insulin-dependent after discharge. Unfortunately, soon after, he began showing signs of liver failure and ultimately underwent liver transplantation. Conclusion: This case highlights two crucial aspects - the importance of screening for autoantibodies prior to initiating an ICI and the necessity for guidelines in diagnosing ICI-T1DM. Given the evidence linking positive GAD Ab to a higher risk of developing DKA and earlier onset ICI-T1DM, it is beneficial to screen patients for these autoantibodies prior to ICI initiation to identify those more susceptible to developing ICIDM1. It may also be beneficial to obtain a C-peptide level prior to initiation to evaluate for endogenous insulin production. Additionally, while several factors support the diagnosis of ICI-T1DM such as recent ICI use, acute DKA presentation, low C-peptide levels, and the need for exogenous insulin, there is currently no specific criteria for the formal diagnosis of ICI-T1DM. Consequently, the decision to continue an ICI remains uncertain until specific diagnostic criteria are established for healthcare providers. Presentation: 6/2/2024