Accelerated partial breast irradiation with external beam three-dimensional conformal radiotherapy. Five-year results of a prospective phase II clinical study.

PURPOSE: The aim of this study was to report the 5-year results of accelerated partial breast irradiation (APBI) using external beam three-dimensional conformal radiotherapy (3D-CRT).

PATIENTS AND METHODS: Between 2006 and 2011, 44 patients with low-risk, stage I-II breast cancer underwent breast-conserving surgery. Postoperative APBI was given by means of 3D-CRT using three to five non-coplanar fields. The total dose of APBI was 36.9 Gy (nine fractions of 4.1 Gy b.i.d.). The mean follow-up time was 58.2 months for surviving patients. Survival results, side effects, and cosmetic results were assessed.

RESULTS: One (2.3%) local recurrence was observed, for a 5-year actuarial rate of 3.7%. Neither regional nor distant failure was observed. Two patients died of internal disease. The 5-year disease-free, cancer-specific, and overall survival rates were 96.3, 100, and 95.1%, respectively. Acute side effects included grade 1 (G1) erythema in 75%, G1 parenchymal induration in 46%, and G1 pain in 46% of patients. No G2 or higher acute side effect occurred. Late side effects included G1, G2, and G3 fibrosis in 44, 7, and 2% of patients, respectively, G1 skin pigmentation in 12%, and G1 pain in 2%. Asymptomatic fat necrosis occurred in 14%. Cosmetic results were rated excellent or good in 86% of cases by the patients themselves and 84% by the physicians.

CONCLUSIONS: The 5-year local tumor control, toxicity profile, and cosmetic results of APBI delivered with external beam 3D-CRT are encouraging and comparable to other APBI series.