What is the target volume for preoperative accelerated partial breast irradiation (APBI)? In regards to Nichols et al. (Int J Radiat Oncol Biol Phys 2010;77:197-202) and Palta et al. (Int J Radiat Oncol Biol Phys 2010, in Press).

摘要

To the Editor: Two recent studies have suggested preoperative accelerated partial breast irradiation (APBI) as an alternative to conventional, post-lumpectomy APBI (1, 2). We commend the authors' efforts in this potentially important area of research, and we hope the following comments regarding target definition will be considered in future studies. To generate pre- and postoperative clinical target volumes (CTVs) for comparison, both studies used a 15-mm margin to expand both the preoperative gross tumor volume (GTV) and the postoperative surgical cavity. It seems to us that the margin used to expand a preoperative GTV should be larger than that used to expand a lumpectomy cavity. As summarized in a recent publication, a 15-mm tumor bed-to-CTV margin, "is based upon data from mastectomy studies which suggest that 90% of sub-clinical multifocal and multicentric disease lies within 30 mm of the edge of index tumour. If, on average, the index tumour is excised with a margin of around 15 mm, a further 15 mm TB-CTV margin might reasonably be expected to encompass the majority of sub-clinical disease" (3). Whether a 30-mm CTV margin should actually be used for preoperative APBI is open to debate. A recent study suggests, for example, that a smaller margin could be considered for tumors without an extensive in-traductal component (4). Nevertheless, to use the same margin pre- and postoperatively seems arguable.