A Composite Assay for HER2-positive Early-stage Breast Cancer Management

This study is testing a combined blood and tissue test to help doctors better manage HER2-positive early breast cancer — specifically to see whether the assay can predict treatment response and guide decisions about treatment after surgery. **You may be eligible if...** - You are 18 or older - You have operable (surgically removable) breast cancer, stage I–III - Your tumor tests positive for HER2 (a protein that drives cancer growth) - You have received or will receive chemotherapy plus trastuzumab (with or without pertuzumab) - You have been followed for at least 3 years after surgery **You may NOT be eligible if...** - You were diagnosed with another invasive cancer before your breast cancer diagnosis - You have been followed for less than 3 years after surgery Talk to your doctor to see if this trial is right for you.