THU353 Late Onset Of Immune Checkpoint Inhibitor-Related Diabetes After 3 Years

Disclosure: S. Avula: None. A. Ahmed: None. M. Salim: None. Z.J. Anderson: None. A. Kumar: None. A. Estrada: None. Background: Immune checkpoint inhibitor-induced diabetes mellitus (ICI-DM) is characterized by acute onset of dramatic hyperglycaemia with severe insulin deficiency following exposure to PD-1/PD-L1 inhibitors. The frequency of type 1 diabetes related to ICIs is estimated to be ∼3.5%. Endogenous insulin secretion is depleted within a few weeks of the clinical onset of diabetes. Moreover, the positive rate for islet-related autoantibodies varies from 5% to 50%. Case: 51-year-old male with a PMH of stage 4 adenocarcinoma of the lung with metastasis to brain, bone, and kidneys was sent to the ED for a POC BG above 700 mg/dl. He was diagnosed with stage 4 lung adenocarcinoma three years prior to the current presentation. He received stereotactic radiotherapy for the brain metastases, Carboplatin/pemetrexed/pembrolizumab x4 cycles, then continued maintenance therapy of pemetrexed/pembrolizumab with the last dose given 3 weeks prior. He had recent evidence of progression, so chemotherapy adjustment was planned, and he started dexamethasone 4mg on the day prior to presentation. Upon ED presentation, he reported new onset polyuria and polydipsia for 1 week accompanied by 10% weight loss over the last 3 months. His vitals were stable. Physical examination was unremarkable. Serum glucose level was found to be 726 mg/dl, Bicarbonate level 28 mEq/L (22-30), creatinine 1.99 mg/dl (baseline 1.2), venous blood PH was 7.29, Bicarbonate 24 mEq/L (24-28), anion gap 15 mEq/L (8-16), B-hydroxybutyrate 2.91 mmol/L (0.02-0.27), sodium 127 mEq/L(135-148) and HbA1c 6.3%. He received normal saline boluses and NPH insulin 15 units SQ, after which his repeat BG level was 426 mg/dl. Given prediabetic Hba1c with recent dexamethasone therapy he was thought to have steroid-induced hyperglycaemia. He was discharged on NPH 15 units daily with Novolog sliding scale. Upon clinic follow-up 1 week later, his BGs did not improve significantly despite stopping steroids. His C-peptide level was low at 0.22 ng/ml (1.10-4.40) with BG 443mg/dl, and GAD -65 antibodies were negative. He continued to have hyperglycaemia while on NPH /Novolog regimen, thus he was switched to Lantus and Novolog regimen with better glycaemic control. He continues to have significant insulin requirements 3 months later. Conclusion: Although the mean interval between the first ICI administration and T1DM development was found to be 201 ± 187 days, the development of type 1 DM may occur with longer intervals from initiating the ICI therapy. In our case, the patient developed new-onset diabetes with low C-peptide after 1,095 days from receiving the first dose of pembrolizumab. On the previous case reports, the presence of GAD-65 antibodies is typically associated with shortened intervals between receiving the ICI therapy and the development of DM. Presentation: Thursday, June 15, 2023