Diabetic Ketoacidosis With the Use of Alpelisib in a Patient With Metastatic Breast Cancer Without Diabetes

Diabetic ketoacidosis (DKA) is a life-threatening medical condition. Alpelisib, a new drug used to treat phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha mutated breast cancer, is reported to cause DKA as a rare adverse effect. We present a case of alpelisib-induced DKA in a patient with metastatic breast cancer without diabetes. An 81-year-old female with a history of hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer presented to the emergency room with clinical features and blood work consistent with DKA. She was started on alpelisib 6 weeks before her presentation to the hospital. She did not have a documented history of diabetes. Upon admission, alpelisib was held, and her blood glucose returned to baseline with intravenous insulin and hydration. Post-discharge, she was managed with sitagliptin. Subsequent attempts to reintroduce alpelisib were associated with hyperglycemia, which led to the permanent discontinuation of alpelisib and the transition to alternative treatment options. Alpelisib causes hyperglycemia by inhibiting the phosphatidylinositol 3-kinase/activated protein kinase-B pathway, which regulates blood glucose levels. This case report illustrates DKA as a presenting symptom and provides potential management options for alpelisib-induced DKA. Hyperglycemia is a frequent adverse effect of alpelisib in patients with diabetes. This case report is unique as our patient developed uncontrolled diabetes within a few weeks after initiation of alpelisib.