Radiation therapy is often used for treating breast cancer patients to ensure that all cancerous cells are destroyed following a lumpectomy, mastectomy or breast-conserving surgery and sometimes prior to surgical treatment in order to shrink a tumor so that it is more easily operable. The three main ways that radiation therapy is delivered include external beam radiation, internal radiation and intraoperative radiation. External radiation therapy is provided by a linear accelerator machine, with the patient receiving outpatient treatment five days a week for up to seven weeks at a time. Internal radiation is a newer approach that is also called brachytherapy or partial-breast radiation. Here, radioactive seeds are placed for a limited time next to where the cancer was excised. This form of treatment takes much less time (one week – or less when provided intraoperatively) and delivers less risk of radiation exposure to healthy parts of the body. Intraoperative radiation therapy (IORT) is a one-time, high dose of radiation delivered by the linear accelerator while surrounding tissue is exposed during the lumpectomy/mastectomy operation. Your physician will thoroughly discuss your treatment options and alternatives based on your specific condition and preferences.