Dr Escobar on CDK4/6 Inhibitor Selection in HR+ Metastatic Breast Cancer

“What we have to rely on [regarding treatment decision-making with CDK4/6 inhibitors] is evaluating retrospective analyses of real-world data and real-world effectiveness [for patients with HR-positive metastatic breast cancer].”

Mauricio Escobar, MD, an associate professor at the O’Neal Comprehensive Cancer Center at the University of Alabama at Birmingham, discussed optimal treatment selection of CDK4/6 inhibitors for patients with hormone receptor (HR)–positive metastatic breast cancer.

Currently, prospective research has not established whether 1 of the 3 FDA-approved CDK4/6 inhibitors in the frontline setting—abemaciclib (Verzenio), ribociclib (Kisqali), and palbociclib (Ibrance)—is efficaciously superior to the others in HR-positive metastatic breast cancer, Escobar began. He noted this is especially because they were each evaluated in separate trials, and cross-trial comparisons are difficult.

However, reviewing retrospective analyses of real-world data and the effectiveness of CDK4/6 inhibitors is currently the most appropriate way when considering optimal treatment for patients, he explained. Of note, a real-world analysis published in the British Journal of Cancer Reports evaluated 2069 patients who received CDK4/6 inhibitors. Results revealed that there was not a statistically significant difference in median progression-free survival (PFS) for each CDK4/6 inhibitor. Specifically, the median PFS for patients treated with abemaciclib was not reached, those treated with palbociclib had a median PFS of 32.0 months (95% CI, 28.9-35.3), and those who received ribociclib had a median PFS of 42.4 months (95% CI, 35.1-52.9). The difference in median overall survival (OS) was also not statistically significant at 37.8 months (95% CI, 31.5-not applicable [NA]), 49.7 months (95% CI, 44.7-54.1), and 54.4 months (95% CI, 47.9-NA) for those treated with abemaciclib, palbociclib, and ribociclib, respectively.

Escobar also added that a real-world analysis based in the United States, published in ESMO Open, did not demonstrate OS differences in the first line with abemaciclib, palbociclib, and ribociclib plus an aromatase inhibitor. After stabilized inverse probability of treatment weighting, the median OS was 64.5 months (95% CI, 55.4-not estimable), 54.6 months (95% CI, 52.6-56.4), and 59.0 months (95% CI, 50.9-66.1) in patients treated with abemaciclib, palbociclib, and ribociclib, respectively.

Based on these 2 retrospective real-world analyses, Escobar concluded that he is comfortable choosing and utilizing any of the 3 CDK4/6 inhibitors as first-line therapy for patients with HR-positive metastatic breast cancer.