1. KPS\>=60

2. histology confirmed invasive breast cancer

3. received breast conservative surgery(wide local excision and axilla dissection, or axillary sentinel node biopsy if sentinel node is negative)

4. surgical margins negative

5. primary tumor ≤5cm in the largest diameter

6. no internal mammary node or supraclavicular node metastases or distant metastasis

7. can tolerate chemotherapy,hormone therapy (if needed) and radiotherapy

8. for patients not need chemotherapy，enrollment date is required no more than 8 weeks from surgery date

9. for patients with chemotherapy first,enrollment date is required no more than 8 weeks from the last date of chemotherapy

10. patients signed written inform consent form

Randomized Study of Hypofractionated and Conventional Fractionation Radiotherapy After Breast Conservative Surgery