Challenges of Renal Function Assessment in Breast Cancer Patients Treated With Abemaciclib: A Case Report.

Abemaciclib, a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor used for hormone-receptor-positive and human epidermal growth factor receptor 2 (HER-2)-negative breast cancer, can lead to elevated serum creatinine without implications on the true renal function. Although clinical trials have shown no increase in other kidney function biomarkers, this may still represent a challenge in cancer patients. We report a case of a 74-year-old female who presented with creatinine and cystatin-C elevation during treatment with abemaciclib without an equivalent decrease in measured glomerular filtration rate (GFR) with renal scintigraphy.