Breast Cancer Coverage from Every Angle

ESMO Breast 2021: Safety Outcomes With Abemaciclib Plus Endocrine Therapy in Early Breast Cancer

By: Julia Fiederlein
Posted: Friday, May 21, 2021

In the phase III monarchE trial, patients with high-risk early breast cancer treated with abemaciclib plus endocrine therapy experienced venous thromboembolic events, elevated aminotransferase levels, and interstitial lung disease more frequently than those treated with endocrine therapy alone. Masakazu Toi, MD, PhD, of the Kyoto University-Graduate School of Medicine, Japan, and colleagues conducted a safety analysis to characterize these adverse events. Their findings, which were presented during the European Society for Medical Oncology (ESMO) Breast Cancer Virtual Congress 2021 (Abstract 440), support the tolerability of this oral CDK4/6 inhibitor in the adjuvant setting.

“Venous thromboembolic events, elevated aminotransferase [levels], and interstitial lung disease were manageable with dose adjustments and co-medications,” the investigators commented. “Results were consistent with the known safety profile of abemaciclib. Most patients experiencing these adverse events could continue abemaciclib.”

Patients with hormone receptor–positive, HER2-negative disease received endocrine therapy with (n = 2,791) or without (n = 2,800) abemaciclib. In those treated with abemaciclib, most venous thromboembolic events were of grade 3 or higher (1.3%); pulmonary embolism was reported most frequently (0.9%). A total of 94.0% of the patients who experienced venous thromboembolic events received anticoagulants, and 19.4% discontinued treatment.

Most elevations in aminotransferase levels of grade 3 or higher were single occurrences (85%), according to the investigators. Of those who experienced this adverse event, 71% had the dose held or reduced, and 16% discontinued treatment. All alanine aminotransferase level increases of grade 3 or higher were reversible with dose modification or treatment discontinuation. Drug-induced liver injury was not reported.

Most interstitial lung disease events were grade 1 (1.4%). Of those who experienced this toxicity, 52% received steroids or antibiotics, and 23% discontinued treatment. Although the prevalence of interstitial lung disease was higher in the Asian population (6.6%), clinically significant adverse events and treatment discontinuations were similar.

Disclosure: For full disclosures of the study authors, visit

By continuing to browse this site you permit us and our partners to place identification cookies on your browser and agree to our use of cookies to identify you for marketing. Read our Privacy Policy to learn more.