LAUSR

Abstract Ribociclib is a selective cyclin-dependent kinase (CDK) 4/6 inhibitor approved in combination with endocrine-based therapy for the treatment of hormone receptor-positive (HR + )/human epidermal growth factor receptor 2-negative (HER2 − ) advanced or metastatic breast cancer. It can significantly prolong the progression-free survival and improve the objective response rate compared with hormone therapy alone. However, the combined regimen results in a higher risk of adverse events, one of them being dermatological reactions. We present a case of late severe skin toxicity in a patient who had received ribociclib for 5 months. The toxicity led to severe pruritus and maculopapular and patchy rash on upper and lower extremities, which completely resolved 1 month after cessation of the drug. We conclude that ribociclib-induced skin toxicity is a noteworthy side effect that can lead to permanent cessation of this drug and is reversible. There are clinical decision dilemmas related to continuation, withholding, or switching CDK4/6 inhibitors, and benefits should be weighed against toxicities and costs.