8% with 90.6% of patients reporting excellent/good cosmesis at 60 months [49] and [50]. A retrospective multi-institutional analysis of nearly 500 patients with 24-month followup demonstrated a 1.2% IBTR with more than 90% of patients having excellent/good cosmesis (48).

Although there are no published randomized comparisons of balloon APBI with WBI, a retrospective matched-pair HDAC inhibitor analysis comparing outcomes from the ASBS Registry with those of WBI patients from the SEER database found no difference in rates of RR or survival at 5 years (65). External beam RT has also been developed as a method to deliver APBI. Two older randomized trials from the United Kingdom found increased rates of LR with partial breast techniques that are inconsistent with today’s standard techniques [17] and [18]. A more recent prospective trial from Italy found reduced rates of acute

toxicities with intensity-modulated RT–based APBI (21). RTOG 0319 was a Phase I/II trial of 52 patients undergoing external beam RT APBI and found the 4-year rate of IBTR to 6%, with only 4% of patients developing Grade 3 toxicity. Although two recent series have documented increased rates of toxicity and poor cosmesis, an interim analysis of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/RTOG 0413 trial evaluating the 1386 patients receiving three-dimensional conformal radiotherapy APBI found no significant toxicity issues at 41 months with a 3% rate of Grade 3 or more fibrosis [52], [53] and [66]. On the contrary, recent analysis of the Randomized Bcl-2 inhibitor clinical trial Trial of Accelerated Partial Breast Irradiation Trial comparing external beam APBI and WBI found that this form of APBI was associated with an increased rate of adverse cosmesis and Grade ½ toxicities with short-term followup (67). Intraoperative therapy, although included in Table 2 as a partial breast technique, should not be grouped

with other APBI modalities in terms of outcomes, toxicities, and guidelines recommendations because of significant differences in the technique. Although initial outcomes from a randomized noninferiority trial comparing intraoperative radiation therapy (IORT) with WBI found no difference in outcomes at 4 years, a more recent update suggested a 2% higher rate Ribonucleotide reductase of IBTR compared with WBI, whereas updates from the Milan trial have found higher than the expected rates of IBTR [20], [68] and [69]. Patient evaluation for APBI should be a multi-disciplinary approach that incorporates the breast surgeon, radiation oncologist, and medical oncologist. Ideally, the patient should be evaluated by a radiation oncologist before or within a few days of surgery. A detailed history should be performed to rule out absolute/relative contraindications for BCT in general or APBI including pregnancy, prior RT to the breast or chest, connective tissue disease, or strong family history (potentially requiring genetic testing).