A Case Of Pembrolizumab-Induced Fulminant Type 1 Diabetes Mellitus In Breast Cancer

Lay abstractImmunotherapy, which can stimulate the immune system to exert anti-tumor effects, has been reported to cause some side effects. Here, we for the first time describe a patient with metastatic breast cancer who rapidly developed a special subtype of diabetes during the immunotherapy. After seven cycles of immunotherapy, a 61-year-old woman developed sudden thirst, polyuria and weight loss. At admission, she was present with extremely high plasma glucose along with a very severe life-threatening complication. Thereafter, she was diagnosed with diabetes related to immunotherapy. In healthy human bodies, insulin is an important hormone to prevent abnormal increase of plasma glucose. However, in our current case, the laboratory results of this patient suggested that immune response activated by immunotherapy completely and rapidly impaired her insulin-generating cells, hence causing the severe diabetes.Aim: The programmed cell death protein-1 (PD-1) inhibitor, pembrolizumab, can exert anti-tumor effects and induce immune-related adverse events. Here, we for the first time describe a patient with metastatic breast cancer who developed fulminant Type 1 diabetes mellitus (FT1DM) during pembrolizumab treatment. Case presentation: A 61-year-old woman received seven cycles of postoperative pembrolizumab combined with tegafur treatment, and developed sudden thirst, polyuria, polydipsia and weight loss. Her laboratory tests contributed to the diagnosis of diabetes ketoacidosis. Her fasting and 2-h postprandial C-peptide levels were both below 0.05 ng/ml, further supporting the diagnosis of FT1DM associated with pembrolizumab administration. Conclusion: Our report highlights the significance of autoimmune diabetes as a rapid and serious adverse event induced by PD-1 inhibitor therapies.