PET/CT for Trop2 ADC Response Evaluation Cancers

This study is using a new type of PET scan (using a probe called 68Ga-MY6349 that targets a protein called Trop-2) to see whether it can predict and track how well a Trop-2-targeted therapy (antibody-drug conjugate) is working in people with metastatic breast cancer. The scans are done before and during treatment. **You may be eligible if...** - You are 18 or older with metastatic breast cancer confirmed by biopsy or imaging - You have previously had systemic treatment for breast cancer - You have at least one measurable lesion on scans - You are scheduled to receive a Trop-2-targeted ADC therapy - Your general health score (ECOG) is 0–1 (fully active or mildly limited) **You may NOT be eligible if...** - You have significantly impaired liver or kidney function - Your life expectancy is less than 3 months Talk to your doctor to see if this trial is right for you.