Dr. Ramaswamy on the Potential for Adjuvant CDK4/6 Inhibition in HR+/HER2- Breast Cancer

Bhuvaneswari Ramaswamy, MD, member, Translational Therapeutics Program, section chief, Breast Medical Oncology, The Ohio State University Comprehensive Cancer Center–James, director, Medical Oncology Fellowship Program in Breast Cancer, The Ohio State College of Medicine, discusses the potential utility of CDK4/6 inhibitors in the adjuvant setting for patients with hormone receptor (HR)–positive, HER2-negative breast cancer.

The phase 3 monarchE trial (NCT03155997) yielded the first positive findings showing that a CDK4/6 inhibitor improved invasive disease-free survival (iDFS) when combined with endocrine therapy as adjuvant treatment for patients with high-risk, early-stage HR-positive/HER2-negative breast cancer. Other studies, such as the PALLAS (NCT02513394) and PENELOPE-B (NCT01864746) trials, failed to demonstrate an iDFS benefit with the addition of a CDK4/6 inhibitor to adjuvant endocrine therapy compared with endocrine therapy alone in this patient population, Ramaswamy says.

Based on these findings, patients with high-risk early-stage breast cancer appear to be the target population for adjuvant CDK4/6 inhibition because these patients tend to have micrometastatic disease, Ramaswamy says. Although longer-term follow-up from the monarchE trial is needed to demonstrate the durability of these responses, CDK4/6 inhibition could have utility in the adjuvant setting for a properly selected patient population, concludes Ramaswamy.