Dynamic changes of blood glucose level during capivasertib treatment in metastatic breast cancer: a case report.

Hyperglycemia is a well-recognized adverse event associated with capivasertib, an oral AKT inhibitor, and may occasionally progress to serious conditions such as diabetic ketoacidosis. We report the case of a 73-year-old woman with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer who developed marked hyperglycemia shortly after initiating capivasertib therapy. Marked hyperglycemia was observed on day 11 of treatment, despite normal baseline levels. Capivasertib was temporarily discontinued, and insulin therapy was initiated. Continuous glucose monitoring revealed transient hyperglycemic episodes occurring exclusively on dosing days, which resolved within approximately 12 h. This pattern suggests a pharmacodynamic correlation and reversible effect of capivasertib on glucose metabolism. Rapid-acting insulin was required only on days when capivasertib was administered. Notably, standard hemoglobin A1c monitoring failed to capture these fluctuations. This case underscores the importance of real-time glucose monitoring and individualized glycemic management during capivasertib therapy, particularly in patients with metabolic risk factors. Early detection and tailored intervention may help prevent severe hyperglycemic complications and facilitate the safe continuation of treatment.