Brachytherapy-based Accelerated Partial Breast Irradiation Provides Equivalent 10-Year Outcomes to Whole Breast Irradiation: A Matched-Pair Analysis.

INTRODUCTION: Although whole breast irradiation (WBI) represents the standard radiotherapy technique in breast conserving therapy, accelerated partial breast irradiation (APBI) has emerged as an option to reduce treatment duration with comparable clinical outcomes. The purpose of this analysis is to present long-term clinical outcomes between WBI and APBI. METHODS: A total of 3009 patients were treated with breast conserving therapy at a single institution between 1980 and 2012. Among them, 2528 patients received WBI and 481 received APBI (interstitial or balloon based). A matched-pair analysis was performed with patients matched by age (±3 years), stage (T-stage vs. T1 vs. T2), and estrogen receptor status (+/-). All patients had a minimum of 12 months follow-up. A total of 274 matches (ratio 1:1) were made. RESULTS: No differences between groups were noted with respect to clinicopathologic features; WBI patients demonstrated a trend for slightly larger tumors (1.3 vs. 1.1 cm, P=0.06). At 10 years, no differences were noted with respect to rates of ipsilateral breast tumor recurrence (4% vs. 4%, P=0.11), regional recurrence (1% vs. 1%, P=0.20), contralateral breast failure (9% vs. 3%, P=0.06), or distant metastases (3% vs. 6%, P=0.47) for WBI and APBI, respectively. In addition, 10-year disease-free survival (93% vs. 91%, P=0.10) and overall survival (83% vs. 75%, P=0.34) were similar. Long-term cosmesis was good to excellent in 94% of WBI patients versus 95% of APBI patients (P=0.78). CONCLUSIONS: At 10 years, no differences in recurrence or survival were found between patients undergoing WBI or brachytherapy-based APBI.