Clinical Study of Breast Conserving Surgery Combined With Intraoperative Radiotherapy for Early Breast Cancer

Inclusion Criteria: 1. Age ≥55 years old； 2. Cytology or histology confirmed invasive breast cancer or intraductal carcinoma in situ (DCIS) with a clinical stage of Tis-1N0M0； 3. Patients who are willing to preserve milk and intend to undergo breast-conserving surgery； 4. If invasive breast cancer is confirmed, the surgical margin negative ≥2mm should be met. If DCIS is confirmed, the surgical margin should be negative ≥3mm； 5. ER≥ 30% and PR≥ 1%, HER2 negative； 6. Voluntary participation in this study, signed informed consent, good compliance, cooperate with follow-up. Exclusion Criteria: 1. Simultaneous diagnosis of bilateral or multifocal breast cancer； 2. Previous ipsilateral breast cancer and/or prior chest wall radiation therapy； 3. There are active connective tissue diseases such as scleroderma and systemic lupus erythematosus in the chest； 4. The investigators did not consider the patient suitable for participation in any other conditions of the study.