Dr. Tolaney on Selecting Patients for CDK4/6 Inhibitors in Breast Cancer

Sara M. Tolaney, MD, MPH, instructor of medicine, Harvard Medical School, attending physician of medical oncology, Dana-Farber Cancer Institute, discusses selecting patients with estrogen receptor (ER)-positive breast cancer for treatment with CDK4/6 inhibitors.

Patient selection is a challenge in ER-positive breast cancer, Tolaney says. There are no established molecular biomarkers that suggest whether a patient would benefit from a CDK4/6 inhibitor or should continue on endocrine therapy. Tolaney says that molecular biomarkers or clinical parameters need to be identified to help select patients who would benefit from CDK4/6 inhibitor therapy.

Looking at the biomarker work that has been done across phase III trials of ER-positive breast cancer, most have yet to determine a molecular biomarker that predicts benefit. In the PALOMA-3 trial, patients with low levels of cyclin E seemed to derive greater benefit from palbociclib (Ibrance) compared to fulvestrant. In a pooled analysis of MONARCH-2 and MONARCH-3, high-risk patients with liver metastases, short treatment-free intervals or low progesterone levels derived significant benefit from the addition of abemaciclib (Verzenio).

Tolaney says that these findings show that patients with visceral or high-risk disease are deriving benefit from CDK4/6 inhibitors. This is an important advancement, she adds, as these patients were traditionally treated with chemotherapy, but can now be treated with endocrine therapy and a CDK4/6 inhibitor.