Accelerated partial breast irradiation with 3-dimensional conformal and image-guided intensity-modulated radiotherapy following breast conserving surgery – 7-Year results of a phase II trial

PURPOSE: To present the 7-year results of accelerated partial breast irradiation (APBI) using three-dimensional conformal (3D-CRT) and image-guided intensity-modulated radiotherapy (IG-IMRT) following breast-conserving surgery (BCS). PATIENTS AND METHODS: Between 2006 and 2014, 104 patients were treated with APBI given by means of 3D-CRT using 3–5 non-coplanar, isocentric wedged fields, or IG-IMRT using kV-CBCT. The total dose of APBI was 36.9 Gy (9 × 4.1 Gy) using twice-a-day fractionation. Survival results, side effects and cosmetic results were assessed. RESULTS: At a median follow-up of 90 months three (2.9%) local recurrences, one (0.9%) regional recurrence and two (1.9%) distant metastases were observed. The 7-year local (LRFS), recurrence free survival was 98.9%. The 7-year disease-free (DFS), metastases free (MFS) and overall survival (OS) was 94.8%, 97.9% and 94.8%, respectively. Late side effects included G1 skin toxicity in 15 (14.4%), G1, G2, and G3 fibrosis in 26 (25%), 3 (2.9%) and 1 (0.9%) patients respectively. Asymptomatic (G1) fat necrosis occurred in 10 (9.6%) patients. No ≥ G2 or higher late side effects occurred with IMRT. The rate of excellent/good and fair/poor cosmetic results was 93.2% and 6.8%, respectively. CONCLUSION: 7-year results of APBI with 3D-CRT and IG-IMRT are encouraging. Toxicity profile and local tumor control are comparable to other series using multicatheter interstitial brachytherapy. Therefore, these external beam APBI techniques are valid alternatives to whole breast irradiation and brachytherapy based APBI.