The rationale for the irradiation of a limited volume of tissue around the surgical bed in place of whole breast irradiation comes from numerous studies that have shown that 80% or more of local relapses after conservative surgery and radiation therapy occur at the original tumor site. Particularly in low-risk patients, a more limited local treatment could be justified. Intraoperative radiotherapy with electrons (IOERT) has the advantages of reducing the radiotherapy course from 5-7 weeks to a single dose given directly in the operating room immediately following tumor resection, and of reducing the course of external radiation treatment needed when IOERT is used as boost. This would overcome some of the constraints that may prevent patients (especially older patients) from having breast-conserving therapy, such as accessibility to a radiotherapy center and the effects of a prolonged treatment course on the patient's social life and financial resources. Moreover, IOERT could minimize some of the potential side effects associated with conventional EBRT because the skin and subcutaneous tissues are not irradiated and the irradiated volumes of lung and heart are significantly reduced. IOERT thus lends itself to implementing the treatment philosophy of partial breast irradiation, but results from the ELIOT randomized Phase III trial are awaited before considering its use as a standard treatment.
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