Association of abemaciclib for metastatic breast cancer with venous and arterial thrombosis

The CDK4/6 inhibitor abemaciclib is a mainstay of treatment for HR-positive breast cancer. However, increased venous thromboembolism (VTE) rates in clinical trial resulted in a black-box warning for this agent. An observational cohort study found that in a real-world setting, abemaciclib for metastatic breast cancer was associated with a VTE rate (7.4%) approimately two-fold greater than the already elevaged rates reported in the MONARCH trials. Patients developing thrombosis on abemaciclib had a significantly higher risk of death compared with patients who did not (HR 2.09; 95% CI 1.07-4.13). The authors conclude that studies evaluating the role of thromboprophylaxis in patients receiving abemaciclib are needed.