Prospective Comparison of Toxicity and Cosmetic Outcome After Accelerated Partial Breast Irradiation with Conformal External Beam Radiotherapy or Single-Entry Multilumen Intracavitary Brachytherapy.

OBJECTIVE: To prospectively characterize toxicity and cosmesis after accelerated partial breast irradiation (APBI) with 3D conformal radiotherapy (3D-CRT) or single-entry multilumen intracavitary brachytherapy.

PATIENTS AND METHODS: Two hundred eighty-one patients with pTis, pT1N0, or pT2N0 (≤3.0 cm) breast cancer treated with segmental mastectomy were prospectively enrolled from December 2008 through August 2014. APBI was delivered using 3D-CRT (N=29) or with a SAVI® (N=176), Contura® (N=56), or MammoSite® (N=20) brachytherapy catheter. Patients were evaluated at protocol-specified intervals, at which time the radiation oncologist scored cosmetic outcome, toxicities, and recurrence status using a standardized template.

RESULTS: Median follow-up is 41 months. Grade 1 seroma and fibrosis were more common with brachytherapy than with 3D-CRT (50.4% vs. 3.4% for seroma, P<0.0001; 66.3% vs. 44.8% for fibrosis, P=0.02), while grade 1 edema was more common with 3D-CRT than with brachytherapy (17.2% vs. 5.6%, P=0.04). Grade 2-3 pain was more common with 3D-CRT (17.2% vs. 5.2%, P=0.03). Actuarial five-year rates of "fair" or "poor" radiation oncologist-reported cosmetic outcome were 9% for 3D-CRT and 24% for brachytherapy (P=0.13). Brachytherapy was significantly associated with inferior cosmesis on mixed model analysis (P=0.003). Significant predictors of reduced risk of adverse cosmetic outcome after brachytherapy were D0.1cc (skin) ≤ 102%, minimum skin distance > 5.1 mm, dose homogeneity index > 0.54, and volume of non-conformance ≤ 0.89 cc. Five-year ipsilateral breast recurrence was 4.3% for brachytherapy and 4.2% for 3D-CRT APBI patients (P=0.95).

CONCLUSIONS: Brachytherapy APBI is associated with higher rates of grade 1 fibrosis and seroma than 3D-CRT but lower rates of grade 1 edema and grade 2-3 pain than 3D-CRT. Rates of radiation oncologist-reported "fair" or "poor" cosmetic outcome are higher with brachytherapy. We identified dosimetric parameters that predict reduced risk of adverse cosmetic outcome after brachytherapy-based APBI. Ipsilateral breast recurrence was equivalent for brachytherapy and 3D-CRT.