Risk of Abemaciclib-induced Liver Injury in Hormone Receptor-positive, HER2-negative Metastatic Breast Cancer: A Retrospective Analysis

Background/Aim: The efficacy of endocrine therapy combined with abemaciclib for hormone receptor–positive, HER2-negative metastatic breast cancer has been established through pivotal clinical trials. However, abemaciclib-induced liver injury (AILI) can be a cause for dose reduction or discontinuation. Therefore, it is critical to understand the risk factors for AILI. Patients and Methods: This retrospective study analyzed data from patients who had received abemaciclib combined with endocrine therapy for metastatic breast cancer as first- or second-line therapy at our hospital between December 2018 and October 2021. Relevant data were extracted from their medical records. Logistic regression analysis was performed to identify characteristics associated with AILI. Results: Of the 52 eligible patients, 12 (23%) received an aromatase inhibitor (AI), and 40 (77%) received fulvestrant, concomitantly with abemaciclib. Fifteen (29%) of the patients developed liver injury after starting abemaciclib. Univariate analysis revealed the following risk factors for AILI: age ≥65 years (p=0.047), fatty liver disease (p=0.047), and concomitant use of an AI (p=0.002). Concomitant use of an AI was identified by multivariate analysis as an independent risk factor for AILI [odds ratio (OR)=10.23, 95% confidence interval (CI)=2.02-51.91, p=0.005]. Conclusion: Concomitant use of an AI could be the most significant factor associated with increased risk of AILI. Future research on the mechanism by which the use of an AI plus abemaciclib can cause liver injury, and prospective studies to validate our findings regarding AILI risk factors, are warranted.