Dr. O'Regan on Emerging CDK4/6 Combinations in Breast Cancer

Ruth O’Regan, MD, professor, division head, Hematology and Oncology, Department of Medicine, University of Wisconsin School of Medicine and Public Health, associate director, Clinical Research, University of Wisconsin Carbone Cancer Center, discusses emerging CDK4/6 inhibitor combinations in breast cancer.

Several ongoing clinical trials are examining CDK4/6 inhibitors in combination with estrogen receptor inhibitors and PI3K/mTOR pathway inhibitors, O’Regan says.

Although the data appear promising, a triplet regimen may not be superior to CDK4/6 inhibitors plus endocrine therapy alone, adds O’Regan. However, direct comparisons are needed to confirm that theory.

Additionally, the triplet regimens are associated with increased but not overlapping toxicities, O’Regan explains.

Ultimately, the risk-benefit ratio with the triplet may not outweigh the impressive responses observed with the doublet in the first-line setting. Instead, PI3K/mTOR inhibition may be better suited for patients who are resistant to endocrine therapy, concludes O’Regan.