Preliminary results of electron intraoperative therapy boost and hypofractionated external beam radiotherapy after breast-conserving surgery in premenopausal women.

PURPOSE: To report the acute and preliminary data on late toxicity of a pilot study of boost with electron intraoperative therapy followed by hypofractionated external beam radiotherapy (HEBRT) of the whole breast.

METHODS AND MATERIALS: Between June 2004 and March 2007, 211 women with a diagnosis of early-stage breast cancer were treated with breast-conserving surgery. During surgery, an electron intraoperative therapy boost of 12 Gy was administered to the tumor bed. Adjuvant local treatment was completed with HEBRT, consisting of a course of 13 daily fractions of 2.85 Gy to the whole breast to a total dose of 37.05 Gy. Acute toxicity of the breast was evaluated at the end of HEBRT and at 1 month of follow-up. Late toxicity was recorded at 6 and 12 months of follow-up.

RESULTS: We report the data from 204 patients. The maximal acute skin toxicity was observed at the end of HEBRT (182 patients evaluable) with 7 (3.8%) Grade 3, 52 (28.6%) Grade 2, 123 (67.6%) Grade 1, and no Grade 0 or Grade 4 cases. A total of 108 patients were evaluated for late toxicity. The recorded late skin toxicity was Grade 4 in 1 patient (0.9%), Grade 3 in 1 patient, and Grade 2 or less in 106 patients (98.2%).

CONCLUSIONS: The results of this study have shown that electron intraoperative therapy followed by HEBRT allows for the delivery of a high dose to the tumor bed and an adequate dose to the whole breast. This treatment is feasible, compliance is high, and the rate of acute toxicity and the preliminary data on chronic toxicity seem acceptable.