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ESMO 2017: Adding Abemaciclib to Endocrine Therapy for Advanced Breast Cancer

Based on the interim analysis of the MONARCH 3 trial, the addition of abemaciclib to endocrine therapy extended progression-free survival compared with endocrine therapy alone in patients with metastatic breast cancer. Angelo Di Leo, MD, of the Hospital of Prato, Istituto Toscano Tumori, Italy, presented the findings of this randomized phase III trial at the 2017 European Society for Medical Oncology (ESMO) Congress (Abstract 236O_PR) in Madrid.

“This is the third study demonstrating that the combination of endocrine therapy with a [cyclin-dependent kinase (CDK)] 4/6 inhibitor is better than endocrine therapy alone,” said Dr. Di Leo in an ESMO press release. “Abemaciclib reduced the risk of disease progression by 46%.”

The trial included nearly 500 patients from 22 countries who had never been treated for metastatic disease. The objective response rate in those with measurable disease was 59% with abemaciclib versus 44% with endocrine therapy alone. The median progression-free survival was not reached in the abemaciclib arm, but the results showed approximately a 46% reduction in the relative risk.

In addition, the data may help to distinguish benefit of such therapy among subgroups of patients. For example, those with liver metastases experienced a benefit from the addition of abemaciclib, whereas those with bone metastases alone or indolent disease may benefit from endocrine therapy alone, perhaps reserving the use of a CDK4/6 inhibitor for a later line of treatment for metastatic disease.