ABSTRACT

For most patients with early-stage breast cancer, a long-established alternative to mastectomy is breast conservation therapy, in which a segmental mastectomy (lumpectomy) is performed, followed by irradiation of the ipsilateral breast (Fisher et al. 2002; Veronesi et al. 2002; Horiguchi et al. 2002; van Dongen et al. 2000; Abe et al. 1995; Holli et al. 2001; Liljegren et al. 2000; Clark et al. 1996; Forrest et al. 1996). As with any irradiation technique, for breast radiotherapy (RT), it is desirable to administer dose uniformly throughout the planning target volume (PTV), limit high-dose spots that otherwise result in a poor cosmetic outcome (Buchholz et al. 1997; Gray et al. 1991; Moody et al. 1994; Taylor et al. 1995; Cheng, Das, and Baldassarre 1994), and to adequately limit the dose received by thoracic organs at risk (OARs) so as to minimize the risk of treatment-related complications (Fisher et al. 1989; Lingos et al. 1991; Wallgren 1992). Achieving breast dose uniformity is challenging given the irregular size and shape of the breast, and inter-and intrafractional variations during breast RT. Ÿe positioning and sparing of OARs also complicates e¢orts toward target dose uniformity. Another major concern with

breast RT is radiation doses to OARs. Ÿe inter-and intrafractional variations necessitate large margins to extend clinical target volume (CTV) to PTV that, in turn, increase doses to OARs and thereby  radiation-related toxicities. Motivated by the need to improve target dose uniformity and to reduce dose to OARs, technology and methodology for breast RT have been advancing rapidly in recent years. In this chapter, a review is presented of these challenges as well as the techniques developed to overcome them, among these being intensity-modulated RT (IMRT; Mihai et al. 2005; Hong et al. 1999; Teh et al. 2001; van Asselen et al. 2001; Partridge et al. 2001; Hurkmans et al. 2002; Cho et al. 2002; Lo et al. 2000; Vicini et al. 2002) and image-guided RT (IGRT; Ja¢ray 2007; Morrow et al. 2007; Weed et al. 2004), which are the two most important enabling technologies for adaptive RT.