MammoSite, for early stage breast cancer with tumors less than 3 cm, reduces the length of radiation therapy without reducing effectiveness. MammoSite therapy internally delivers radiation directly to the tissue surrounding the original tumor, where recurrence is most likely, minimizing radiation exposure to healthy tissue.  MammoSite therapy is a balloon catheter that is inserted into the cavity created by a lumpectomy (the surgical removal of a a breast tumor.)