Euglycemic Diabetic Ketoacidosis under Empagliflozin during Neoadjuvant Pembrolizumab and Chemotherapy in Early Breast Cancer: A Case-Report.

Introduction: Empagliflozin is a widely used medication for type 2 diabetes mellitus (T2DM) that can increase the risk for diabetic ketoacidosis (DKA) among susceptible patients. Pembrolizumab cancer immunotherapy can lead to immune-related adverse events such as diabetes mellitus (DM), with most of the reported cases presenting with hyperglycemic DKA. However, euglycemic DKA (eDKA) can also occur and is particularly dangerous because of the potential for delayed or misdiagnosis of DKA. Case Presentation: We report a breast cancer patient with DM receiving empagliflozin and basal insulin therapy, presenting with eDKA during neoadjuvant chemotherapy and pembrolizumab immunotherapy. The patient's condition deteriorated into a comatose state, which necessitated intubation and mechanical ventilation. She improved under intravenous fluids and insulin, returned to full consciousness, was extubated and discharged from the intensive care unit. She underwent surgery and radiotherapy and was most recently seen in the oncology unit with an excellent performance status again. Conclusion: To the best of our knowledge, we report the first case of fulminant eDKA in a breast cancer patient treated with empagliflozin, neoadjuvant chemotherapy and pembrolizumab immunotherapy according to the Keynote 522 regimen, despite basal insulin therapy initiation, highlighting the need to use this combination with caution.