Real-world Benefit Of Combination Abemaciclib And Endocrine Therapy For Metastatic Breast Cancer And Correlation With Neutropenia

Objective:To investigate whether early neutrophil reduction is associated with the efficacy of abexile plus endocrine therapy for advanced breast cancer.Methods:This study included HR‐positive,HER2‐negative advanced or m BC patients who were treated with abemaciclib plus endocrine therapy,mainly fulvestrant,between 1 January 2020 and1 August 2022.Progression ‐free survival(PFS)was determined using Kaplan–Meier analysis.The predictive value of absolute neutrophil count(ANC)and neutrophil‐to‐lymphocyte ratio(NLR)for PFS were explored using Cox regression models.Both ANC and NLR were used as a time ‐ dependent variable.Results:In total,90 patients were included with median PFS of 7 months(95% CI 18.93–NR).Lower ANC was correlated with decreased risk of progression(HR0.84,95% CI 0.71–0.97,p=0.008).There was no significant association between NLR and the risk of disease progression(HR 1.07,95% CI0.97–1.18,p=0.203).Conclusion:The effectiveness of abemaciclib and endocrine therapy in the treatment of HR‐positive,HER2‐negative m BC in the real‐world setting is similar to the efficacy reported in the MONARCH-1trial.Patients with lower neutrophil count may have a lower risk of early disease progression.