A system provided for delivering Accelerated Partial Breast Irradiation (APBI) and for delivering a boost to standard whole-breast irradiation (WBI) for the treatment of breast cancer that significantly reduces the risks of adverse cosmetic outcomes and toxicities. This is achieved by a method and device for delivering a uniform radiation dose to the target volume with significantly reduced dose to the non-target volume, skin and chest wall of the ipsilateral breast, and virtually no dose to the contralateral breast, lungs, and heart.
