Time-Compressed 2-Day Brachytherapy Accelerated Partial Breast Irradiation Versus Hypofractionated Whole-Breast External Beam Radiation for Early-Stage Breast Cancer: A Comparative Analysis of Clinical Effectiveness, Late Toxicities, and Cosmesis

Short course, time-compressed radiation therapy is increasingly being adopted for early-stage breast cancer. We performed a propensity-score matched-pair analysis comparing time-compressed 2-day brachytherapy-based accelerated partial breast irradiation [2d-APBI] and hypofractionated [HFx] whole-breast radiation therapy to assess clinical effectiveness, late toxicities, and cosmetic outcome. Between March 2004 and January 2015, appropriately selected patients treated with single-channel balloon-based 2d-APBI [700 cGy BID x 4] or whole-breast 3-week HFx [266 cGy daily x 16] were reviewed as part of an IRB-approved analysis. Follow-up [FU] was ≥ 1 year for all patients. Propensity-score matching (1:1 ratio) using age +/- 5 years, clinical stage and ER status was performed resulting in 84 patients (42 pairs) for analysis. Ipsilateral breast tumor recurrence (IBTR), regional recurrence (RR), distant metastasis (DM), contralateral breast cancer (CLBC), disease-free survival (DFS), cause-specific survival (CSS), and overall survival (OS) were compared by Kaplan-Meier. Patient and disease traits were computed using Pearson's chi-square test and paired t-test. Toxicities were scored using CTCAE v4.0. Cosmetic rating was scored via the Harvard criteria. Mean FU for all patients was 5.4 years [7.7 years for 2d-APBI vs 3.1 years for HFx, P < 0.001]. This difference in median follow-up was expected considering era of implementation of each technique (2d-APBI: 2004; HFx: 2009). There was no statistically significant difference in median age, T-stage, grade, nodal status, margins, biomarker status, or menopausal state between the two treatment groups. More HFx compared to 2d-APBI patients received endocrine therapy [80% vs 58% P = 0.036]. Comparing 2d-APBI and HFx, there were no statistically significant differences in IBTR [0% vs 0%], RR [0% vs 0%], DM [2.4% vs 2.4% P = 0.993], CLBC [0% vs 2.4% P = 0.317], DFS [97.6% vs 97.6% P = 0.993], CSS [100% vs 100%], and OS [97.4% vs 88.9% P = 0.72] at five years. Late toxicities analyzed included skin pigment changes, edema, pain, induration, telangiectasias, seroma, and fat necrosis. No grade 3 toxicities were noted except for a 2% versus 0% rate of telangiectasias for 2-d APBI versus HFx, respectively (P = 0.027). Neither seroma nor fat necrosis had significant difference between the two regimens. Cosmetic outcomes were good to excellent in the majority of patients with no statistical difference between the 2 schemes [2d-APBI of 87% good to excellent vs HFx of 96% P = 0.393]. At 5 years, 2d-APBI and Hfx had similar clinical effectiveness, late toxicities, and cosmetic outcomes, with a dramatic reduction in the length of therapy for time-compressed short-course brachytherapy (∼48 hours compared with ∼3-4 weeks). Further FU for patients treated with both techniques are needed to substantiate these findings.