A Multi-center Real-world Efficacy and Safety of Trastuzumab-deruxtecan in Advanced Gastric Cancer

This is a real-world study looking at how effective and safe trastuzumab deruxtecan (T-DXd) is in patients with advanced HER2-positive stomach or gastroesophageal junction cancer who have already received at least two prior lines of treatment. Rather than testing a new drug, it is studying how a current drug performs in everyday clinical practice. **You may be eligible if...** - You are 19 years or older - You have been diagnosed with metastatic, recurrent, or unresectable HER2-positive stomach or gastroesophageal junction adenocarcinoma - Your tumor shows HER2 positivity (IHC 3+ or IHC 2+ with ISH positive) - You received trastuzumab deruxtecan as third-line or later treatment **You may NOT be eligible if...** - Your tumor is HER2-negative - You received trastuzumab deruxtecan as a first- or second-line treatment in a clinical trial - You did not consent to participate Talk to your doctor to see if this trial is right for you.