Clinical Management of Potential Toxicity of Abemaciclib and Approaches to Ensure Treatment Continuation

Abstract

INTRODUCTION: The association between abemaciclib dose reduction and treatment adherence is not clear. In this study, we examined real-world data of Japanese patients with advanced breast cancer (ABC) to determine how abemaciclib dose reduction is related to treatment continuation. METHODS: This retrospective observational study involved 120 consecutive patients with ABC who received abemaciclib from December 2018 to March 2021. The time to treatment failure (TTF) was estimated using the Kaplan-Meier method. Univariate and multivariate analyses were performed to identify factors associated with a TTF of >365 days (TTF365). RESULTS: According to the dose reduction during treatment, the patients were classified into 100, 200, and 300 mg/day abemaciclib groups. The 300 mg/day group had a TTF of 7.4 months, whereas the 100 and 200 mg/day groups had significantly longer TTFs (17.9 and 17.3 months, respectively; P = 0.0002). In this study, relative to the 300 mg/day arm, TTF was improved in 200mg/day arm and 100 mg/day arm (hazard ratio [HR], 0.55; 95% confidence interval [CI], 0.33-0.93) and [HR], 0.37; 95% CI, 0.19-0.74). For patients who received 300mg/day of abemaciclib dose arm, 200mg/day, and 100mg/day, the median TTF was 7.4 ,17.9 and 17.3 months. The frequently reported adverse effects (AEs) were anemia, increased blood creatinine levels, diarrhea, and neutropenia (90%, 83%, 83%, and 75% of the patients, respectively). Neutropenia, fatigue, and diarrhea were the top AEs causing dose reduction. A multivariate analysis that examined factors associated with achieving TTF 365 confirmed that dose down was an important factor (odds ratio: 3.95, 95% confidence interval: 1.68-9.36, P = 0.002). CONCLUSIONS: In this study, the 100 and 200 mg/day groups had a longer TTF than the 300 mg/day group, and dose reduction was identified as an important factor in achieving longer TTF.