This study is a national multicenter phase II prospective clinical trial to enroll low-risk breast cancer treat with breast-conserving surgery. All eligible patients will receive ABPI to a total dose of 40Gy, in 10 fractions, 4Gy/fx/day, within 2 weeks. Intensity modulated radiation therapy (IMRT) technique is used. During Follow up, the locoregional recurrence,survival,acute and late adverse events,and quality of life will be prospectively evaluated.
