A Single-center, open, prospective study，for analyzing the local recurrence rate, the incidence of incision complications and the aesthetic effect of intraoperative radiotherapy in early breast cancer patients after breast-conserving surgery.
Age ≥55 years old；
Cytology or histology confirmed invasive breast cancer or intraductal carcinoma in situ (DCIS) with a clinical stage of Tis-1N0M0；
Patients who are willing to preserve milk and intend to undergo breast-conserving surgery；
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；
Simultaneous diagnosis of bilateral or multifocal breast cancer；
Previous ipsilateral breast cancer and/or prior chest wall radiation therapy；
There are active connective tissue diseases such as scleroderma and systemic lupus erythematosus in the chest；
The investigators did not consider the patient suitable for participation in any other conditions of the study.