Optimal Application Timing of ADC Drugs for Advanced Breast Cancer

This study plans to initiate a prospective, randomized controlled trial to investigatethe optimal timing of antibody drug conjugate (ADC) therapy in the management of advancedHuman Epidermal Growth Factor Receptor 2 (HER2)‐negative breast cancer.Primary Objective:To compare the difference in PFS2 (Time from randomization to disease progression aftersecond therapy) between antibody‐drug conjugate (ADC) followed by chemotherapy versuschemotherapy followed by ADC in the treatment of advanced HER2‐negative breast cancer.Secondary Objectives:To compare overall survival (OS), adverse events, patient‐reported outcomes, andcost‐effectiveness between the two treatment sequences. Additionally, to identifypotential biomarkers predictive of benefit from frontline ADC therapy.