CDK4/6 Inhibitor-Mediated Cutaneous Toxicity in Breast Cancer

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are currently in widespread use for the treatment of both advanced metastatic and early-stage hormone receptor (HR)-positive, human epidermal growth factor receptor (HER2)- negative breast cancer. Clinical studies in the metastatic setting have demonstrated a survival benefit with the use of ribociclib. Both abemaciclib and ribociclib have shown significant improvements in invasive disease-free survival in high-risk early-stage breast cancer. Hematologic adverse events are well characterized with the three currently approved CDK4/6 inhibitors, namely palbociclib, abemaciclib, and ribociclib. Among non-hematologic toxicities, there is a paucity of information regarding cutaneous adverse events related to these three medications. In this case report, we seek to describe the incidence, time to onset, and management of CDK4/6-mediated cutaneous adverse events.