This study focuses on patients with HER2-positive breast cancer, a type of cancer with a specific protein (HER2) that promotes cancer growth. The trial compares two treatments: one group receives only HER2-targeted therapy, while the other group receives both HER2-targeted therapy and radiotherapy (using radiation to kill cancer cells). This is a Phase III study, meaning it aims to confirm the effectiveness of treatments. The study includes patients who have had breast-conserving surgery and are at early-stage, low-risk. The aim is to see if skipping radiotherapy is safe and effective for these patients. The study is important because it could help reduce the side effects and costs linked to radiotherapy if it turns out not to be necessary for some patients.

• Study Duration: Participants will be followed for several years.
• Eligibility: Adults aged 40 or older with HER2-positive breast cancer who have had surgery and specific treatments.
• Considerations: Potential risks include cancer recurrence; benefits include avoiding radiotherapy side effects.