A Retrospective Observational Study of Safety and Effectiveness of Abemaciclib in Chinese Patients with Breast Cancer.

INTRODUCTION

Abemaciclib is approved in China for treating hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer (ABC) and early breast cancer (EBC). This retrospective, real-world observational study evaluated the safety and effectiveness of abemaciclib among Chinese patients with EBC/ABC.

METHODS

The study included patients from the National Anti-Tumor Drug Surveillance System who initiated abemaciclib between April 2021 and December 2022, with ≥ 1 post-treatment visit by June 2023. Primary objectives were to describe patient characteristics and prevalence of adverse events (AEs) of interest. Real-world progression-free survival (rwPFS) and overall survival (OS) among patients with ABC were exploratory objectives.

RESULTS

Overall, 3423 patients (EBC 619, ABC 2804) were included (3407 [99.5%] female and 16 [0.5%] male); most initiated abemaciclib at 150 mg twice daily (EBC 79.9%, ABC 68.9%). Among patients with EBC, 92.2% had positive lymph nodes. Among patients with ABC, 45.2%, 25.4%, and 29.3% received abemaciclib as first-line, second-line, and third-or-later-line therapy, respectively. Treatment discontinuation occurred in 5.2% of patients with EBC and 25.1% with ABC, and dose reduction in 21.2% and 20.1%, respectively. AEs of interest occurred in 60.7% of patients with EBC and 57.3% with ABC, mostly grades 1-2 in severity; the most common AE of interest was neutropenia (39.9% and 34.5% in patients with EBC and ABC, respectively). Discontinuation due to AEs occurred in 2.4% of patients with EBC and 4.1% with ABC. Among patients with ABC receiving abemaciclib as first-line, second-line, and third-or-later-line therapy, 12-month rwPFS rates were 80.5%, 72.7%, and 57.3%, and OS rates were 90.5%, 84.3%, and 73.0%, respectively. Effectiveness was consistent across menopausal status and endocrine therapy subgroups.

CONCLUSIONS

In this largest real-world study of abemaciclib in China to date, abemaciclib was well tolerated with no new safety signals, and its effectiveness was consistent with prior trials, confirming its positive benefit-risk profile in real-world settings.