Optimal Application Timing of ADC Drugs for Advanced Breast Cancer

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