ctDNA Monitoring in Early Breast Cancer

Inclusion Criteria: 1. Patients aged 18 to 80 years old 2. Histologically proven primary breast cancer with clinical stage I-III 3. Patients with neoadjuvant therapy, and/or radical surgery/breast conserving surgery, adjuvant chemotherapy and target therapy (Her2+), radiotherapy (if indicated). 4. Expected to achieve R0 resection. 5. Estimated lifetime is more than 3 months. 6. Signed Informed Consent Form 7. Consent to provide research blood samples. Exclusion Criteria: 1. Patients intended to receive adjuvant chemotherapy with Eastern Cooperative Oncology Group (ECOG) performance status 3, 4 or 5. 2. Patients intended to receive postoperative radiotherapy with Eastern Cooperative Oncology Group (ECOG) performance status 5. 3. Prior diagnosis of cancer in the previous 5 years, other than for basal cell carcinoma of the skin or cervical carcinoma in situ. 4. Presence of any systemic illness incompatible with participation in the clinical trial or inability to provide written informed consent.