475eP Ethnicity-based comparative analysis of objective response rate in 30,000 HR+/HER2- metastatic breast cancer patients treated with CDK4/6 inhibitors (palbociclib, ribociclib, abemaciclib): A real-world meta-analysis

Abstract

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), with endocrine therapy, are standard treatment for hormone receptor-positive, HER2-negative metastatic breast cancer (HR+/HER2-MBC), with randomised controlled trials (RCTs) suggesting significant improvements in Objective response rate (ORR). As Ethnic minorities are underrepresented in clinical trials, this meta-analysis compares ORR with Palbociclib, Abemaciclib, and Ribociclib across ethnic groups. Method(s): Following PRISMA guidelines, MEDLINE and Embase were searched; 116 studies were included (Palbociclib: 67, Abemaciclib: 29, Ribociclib: 20). Parenthetical values represent 95% confidence intervals (CI). Result(s): Palbociclib Analysis of 31 studies shows pooled ORR varied by ethnicity. Black (BL) patients had the lowest ORR at 25% (17-23). Asian (AS) and White (WH) populations had comparable rates: 34% (27-42) and 34% (28-65), with an overall ORR of 35% (29-41). Substantial heterogeneity was observed (I2 = 93%, tau2 = 0.51). Abemaciclib A total of 4,715 patients were analysed (AS: 2,429; WH: 2,223; BL: 32; MX: 21). WH patients exhibited the highest ORR at 41.9% (14.9-68.9; p = 0.51). Abemaciclib A total of 4,715 patients were analysed (AS: 2,429; WH: 2,223; BL: 32; MX: 21). WH patients exhibited the highest ORR at 41.9% (14.9-68.9; p = 0.51). Abemaciclib A total of 4,715 patients were analysed (AS: 2,429; WH: 2,223; BL: 32; MX: 21). WH patients exhibited the highest ORR at 41.9% (14.9-68.9; p 2 = 97.8% and 98.0%, respectively). ORR was not pooled for BL patients due to insufficient reporting. Ribociclib 4157 patients (WH: 2189; AS: 1514; BL: 131; MX: 42) were included. AS had the highest ORR at 52.4% (46.4-58.5; Q = 28.52, df = 4, p = 97.8% and 98.0%, respectively). ORR was not pooled for BL patients due to insufficient reporting. Ribociclib 4157 patients (WH: 2189; AS: 1514; BL: 131; MX: 42) were included. AS had the highest ORR at 52.4% (46.4-58.5; Q = 28.52, df = 4, p 2 = 86.0%), reflecting between-study differences not random error. Conclusion(s): This meta-analysis reveals numerical differences in ORR and toxicity by ethnicity, though meta-regression did not identify ethnicity as an independent predictor. AS showed higher haematological toxicity, while ORR patterns varied. Legal entity responsible for the study: Olivia Benny. Funding(s): Has not received any funding. Disclosure: All authors have declared no conflicts of interest. Copyright © 2026