Laura S. Muñoz-Arcos, MD

Testing strategies to better predict response to CDK4/6 inhibitors in patients with hormone receptor-positive metastatic breast cancer.

Impact

The most common type of metastatic breast cancer is driven by natural hormones – estrogens and progesterone – and classified as ER and PR-positive. This subtype is often treated with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, a class of medications that target specific growth enzymes in the tumor cells, in combination with hormone suppressing therapies. Approximately half of the hormone-receptor positive metastatic breast cancers also produce the growth promoting protein HER2. This is important because prior studies have shown that the response to CDK4/6 inhibitors may be reduced in the presence of HER2.

Despite improvements in survival with CDK4/6 inhibitors, cancer tumor cells can still become resistant to these drugs, grow, and spread. Currently, there is no test that predicts who will respond to the CDK4/6 inhibitors. Breast cancer cells that travel in the blood stream (also known as circulating tumor cells) offer an appealing way to study the presence of HER2 and its relationship with response to CDK4/6 inhibitors. These cells are obtained through a peripheral blood draw, limiting complications of repetitive surgical biopsies.

What’s next

Dr. Muñoz-Arcos’ Conquer Cancer research supported by BCRF focuses on isolating circulating tumor cells from the blood of patients with hormone-receptor positive metastatic breast cancer before starting on CDK4/6 inhibitors. Her team will evaluate whether the detection of the HER2 protein in circulating tumor cells can predict a reduced response to CDK4/6 inhibitors. The team anticipates that the study results will provide the basis for using the HER2 protein detection in circulating tumor cells as a blood test to predict the response to CDK4/6 inhibitors in hormone receptor-positive metastatic breast cancer.