RC48-ADC in HER2-low Advanced Breast Cancer

This study is testing a targeted drug called RC48-ADC in women with advanced or metastatic breast cancer that has low or very low levels of a protein called HER2. Unlike standard HER2-positive breast cancer treatments, this trial focuses on patients whose tumors have only a trace amount of HER2. The goal is to see if this drug can slow or stop cancer growth. **You may be eligible if...** - You are a woman aged 18 or older with advanced or metastatic breast cancer - Your cancer has low or very low HER2 levels (confirmed by a test) - You have not previously received an antibody-drug conjugate treatment - You have had at most one prior chemotherapy for advanced disease - Your general health is good (ECOG score of 0 or 1) **You may NOT be eligible if...** - You have had a blood clot (thromboembolism) in the past - You have uncontrolled conditions like diabetes, high blood pressure, or lung disease - You have active infections needing treatment - You are pregnant or breastfeeding - Your cancer has spread to the brain Talk to your doctor to see if this trial is right for you.