Abstract Disclosure: N. Kalara: None. P. Rios: None. F. Vendrame: None. Introduction: Alpelisib is a p110a subunit phosphatidylinositol-3kinase inhibitor (PI3K) approved for treating hormone receptor-positive, human epidermal growth factor receptor 2-negative, PIK3CA mutated, advanced or metastatic breast cancer. PI3K signaling is essential for the metabolic action of insulin and the inhibition of p110a subunit is associated with hyperinsulinemia and hyperglycemia. In the combination (Alpelisib-Fulvestrant) arm of phase III SOLAR-1 study the all-grade incidence of hyperglycemia was 63%, but diabetic ketoacidosis (DKA) was also observed and reported in 0.7% of patients. To the best of our knowledge, less than 10 cases of Alpelisib-induced DKA have been reported in the literature. Here we describe an additional case. Case Description: A 62-year-old female with a history of metastatic breast cancer, hypertension, and prediabetes, presented with 3 days of nausea, vomiting, abdominal pain, weakness, polyuria, and polydipsia. Fifteen days prior to the presentation the HbA1c was 6.1% for which she was started on metformin 500 mg daily. Alpelisib 150 mg PO BID and Fluvestrant (Estrogen receptor antagonist) were also started the same day. The patient was told to stop the PIK3 inhibitor if the blood glucose increased above 200 mg/dL. The review of system was positive for fatigue, decreased appetite, malaise, 5 lbs weight loss during the previous week, and headache. She had no family history of any endocrinologic disease. The physical exam was unremarkable with no signs of insulin resistance. Laboratory tests revealed pH 7.31 (7.35-7.45), HCO3 10 mmol/L (22-26), PCO2 21 mmHg (35-45), glucose 884 mg/dL (74-106), sodium 120 mmol/L (136-145), K 5.2 mmol/L (3.5-5.1), Cl 93 mmol/L (98-107), CO2 7 mmol/L (21-32), anion gap 22 mmol/L (5-15), GFR 30 mL/min/1.73m2 (>60), Cr 1.80 mg/dL (0.5-1.02), BUN 43 mg/dL (7-18), beta-hydroxybutyrate 3 mmol/L (0.4-0.5), HbA1c 9.2% (4.2-5.6). Additional testing revealed C-peptide 2.3 ng/ml (1.1-4.4) with glucose 397 mg/dL. Results suggested a combined DKA and hyperosmolar hyperglycemic state (HHS). Alpelisib was discontinued and the patient was managed with insulin drip, fluids, electrolyte replacement, and eventually transitioned to a basal-bolus regimen (0.5U/kg). The patient was discharged on metformin and Insulin glargine with the recommendation to follow up with endocrinology and oncology. Conclusion: Our case highlights the importance of blood glucose and HbA1c screening before starting Alpelisib with emphasis on a multidisciplinary approach to monitor blood glucose levels to prevent DKA. Reference: 1. Farah SJ, Masri N, Ghanem H, Azar M. Diabetic ketoacidosis associated with alpelisib treatment of metastatic breast cancer. AACE Clin Case Rep. 2020;6(6):e349-e351. doi: 10.4158/ACCR-2020-0452 Presentation: Thursday, June 15, 2023
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