Real-world analysis of eribulin sequencing and outcomes in advanced breast cancer: An LMIC cohort study focusing on line of therapy and prior cyclin-dependent kinase 4/6 inhibitor exposure.

Abstract

e13050 Background: In Low-and-Middle-Income Countries (LMICs), eribulin is often a late-line salvage. With increasing use of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), optimal placement of eribulin requires investigation. We evaluated outcomes based on line of therapy and prior CDK4/6i exposure. Methods: Retrospective analysis of 99 patients with mBC treated with eribulin in India (2019– 2023). Primary endpoint was median progression-free survival (mPFS). Subgroups compared early-line (L2-3) vs. late-line (L4+) and prior CDK4/6i exposure using Mann-Whitney U tests. Median Overall Survival (mOS) was not calculated due to data immaturity, compounded by the inherent challenges of loss to follow-up and the lack of integrated survival registries in an LMIC setting. Results: Median age was 52 years; 79.8% had visceral metastases; 96% had ECOG PS 0-1. Overall mPFS was 4.04 months (mean 5.3 cycles). Line of Therapy: L2-3 use (72.7%) showed significantly longer mPFS vs. L4+ (4.88 vs. 2.14 months; p < 0.001). CDK4/6i Sequencing: Patients post-CDK4/6i (42.4%) achieved mPFS of 5.22 months vs. 4.07 months in CDK4/6i-naive patients (p = 0.02). TNBC Subset: Triple-negative subgroup (n = 23) mPFS was 3.12 months despite 91.3% visceral involvement. CBR and Safety: 6-month clinical benefit rate was 39.4%. Grade 3/4 neutropenia occurred in 31.3% of patients. Conclusions: Eribulin outcomes were significantly influenced by line of therapy, with superior mPFS in earlier-line settings (L2-3). Clinical activity was robust post-CDK4/6i, suggesting eribulin is an effective sequential option following targeted therapy failure in high-risk visceral disease.