Accelerated Partial Breast Irradiation

Rarely since the introduction of breast-conserving therapy in the 1980s has the breast radiation oncology community been so passionately divided and arguing for the introduction of a new concept as for accelerated partial breast irradiation (APBI). The idea looks a priori counterintuitive—limiting the concept of clinical target volume (CTV) and hence the irradiated volume within anatomical breast boundaries. The passion in published opinions possibly comes from a strange mix of financial interest, competition between techniques, and the extensive use of patient’s advertisements and press releases instead of clinical evidence and data (Smith et al. JAMA 307:1827–1837, 2012; Khan et al. JAMA 308:567, 2012). It is striking that in 2016 two articles reviewing the best available evidence, one by Vicini et al. and the other from the Cochrane Library (Vicini et al. Brachytherapy 15:607–615, 2016; Hickey et al. Cochrane Database System Review 7:CD007077, 2016), had exactly opposite conclusions. The former concluded that “Four contemporary trials with over 2000 patients comparing APBI and whole breast irradiation (WBI) have been published and demonstrate no differences in the rates of local/regional recurrence or survival though long-term follow-up is limited to one study. In addition, reductions in the rates of acute and chronic toxicity and improvements in cosmetic outcome were noted in two of these trials.” The latter concluded that “It appeared that local recurrence and 'elsewhere primaries’ (new primaries in the ipsilateral breast) are increased with PBI/APBI (the difference was small), but we found no evidence of detriment to other oncological outcomes. It appeared that cosmetic outcomes and some late effects were worse with PBI/APBI but its use was associated with less acute skin toxicity.” There is one thing most experts would agree on: that almost 25 years after the first mention of partial breast irradiation by Bethune in the Journal of the National Medical Association (Bethune Journal of the National Medical Association 83:768, 800–808, 1991), evidence is now emerging that the APBI paradigm is safe for highly selected patients. This chapter reviews a selection of the available evidence.