Breast-conserving treatment is mainly for patients with breast-conserving intention and no contraindications to breast-conserving treatment: 1. Early stage I and II clinical breast cancer with tumor size belonging to T1 or T2 stage, especially suitable for early stage breast cancer patients whose maximum tumor diameter does not exceed 3 cm and who have appropriate breast volume, appropriate ratio of tumor to breast volume, and who can maintain good breast shape after surgery; 2. Stage III patients (except inflammatory breast cancer) can also be carefully considered after preoperative chemotherapy or preoperative endocrine therapy with adequate stage reduction. Pre-operative chemotherapy or pre-operative endocrine therapy can also be carefully considered after adequate stage reduction. Absolute contraindications to breast-conserving treatment: 1) Previous breast or chest wall radiotherapy to the ipsilateral breast; 2) Extensive lesions or confirmed multicentric lesions with difficulty in achieving negative margins or ideal shape; 3) Positive margins after extensive local excision and negative margins after re-excision; 4) Patients who refuse breast-conserving surgery; 5) Inflammatory breast cancer. Relative contraindications to breast-conserving treatment: 1) active connective tissue disease, especially scleroderma and systemic lupus erythematosus or collagen vascular disease, poor tolerance to radiotherapy; 2) tumor diameter greater than 5 cm; 3) close to or invading the nipple (such as nipple paget’s disease); 4) extensive or diffuse distribution of suspected malignant microcalcification foci.