Circulating Tumor Cells and Treatment De-escalation After Neoadjuvant Therapy for HER2 Positive Breast Cancer

This study investigates whether patients with HER2-positive breast cancer who have a complete response to pre-surgery chemotherapy (no cancer cells found after surgery) can safely skip additional chemotherapy after surgery, using circulating tumor cells (cancer cells found in the blood) as a guide. **You may be eligible if...** - You have HER2-positive breast cancer (hormone receptor positive or negative) - Your cancer is stage I–III - You are receiving pre-surgery chemotherapy plus trastuzumab and pertuzumab - You had surgery after neoadjuvant therapy and achieved a complete pathological response (no remaining cancer) - You are in good overall health (ECOG 0–3) **You may NOT be eligible if...** - You have a contraindication to trastuzumab or pertuzumab - You are receiving adjuvant chemotherapy (hormone therapy is allowed) - You have been diagnosed with a second primary cancer in the last 5 years (except treated non-melanoma skin cancer or in-situ cervical cancer) Talk to your doctor to see if this trial is right for you.