Accelerated partial breast irradiation using external beam conformal radiation therapy: a review

Lumpectomy followed by whole breast radiation therapy (i.e. breast conservation therapy (BCT)) is the standard of care for management of early stage breast cancer. However, its utilization has not been maximized because of a number of reasons including the logistic issues associated with the 5-6 weeks of radiation treatment. Also, pathological and clinical data suggest that most ipsilateral breast cancer recurrences are in the vicinity of the lumpectomy. Accelerated partial breast irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin, rather than the whole breast with higher doses of radiation in a shorter period of time. There has been growing interest for APBI and various approaches have been developed and are under phase I-III clinical studies. This paper reviews external beam conformal radiation therapy (EBCRT) as a possible technique to APBI. The various EBCRT approaches such as 3D conformal radiation therapy, IMRT, proton therapy, tomotherapy, and volumetric arc therapy are discussed. Issues with the implementation of these techniques such as target volume delineation and organ motion are also presented. It is evident that EBCRT has potential for APBI of a selected group of early breast cancer patient. However, issues with setup errors and breathing motions need to be adequately addressed.