Acute and late side effects for intraoperative electron radiotherapy during breast-conserving surgery of breast cancer.

Abstract

94 Background: Intraoperative boost irradiation as part of breast-conserving therapy is a perfect method to adequately capture the high risk tumor relapse area. The most homogeneous dose distribution is achieved with electrons. Intraoperative radiotherapy (IOERT) as a boost for breast cancer releases a high single dose of radiation to the breast tissue; therefore acute toxicity is of particular attention. To date there is only inadequate information available on breast cancer patients treated with IORT using electrons applied as a boost. We therefore analyzed the acute toxicity and late side effects after radiotherapy with 10 Gy as a boost with a minimum follow-up of 3 months. Methods: A total of 385 patients treated with IOERT (10 Gy with 5, 7 and 9 MeV electrons) with a dedicated robotic linac (NOVAC 7, New Radiant Technology, Aprilia, Italy) to the tumor bed during breast-conserving surgery as a boost followed by whole-breast radiotherapy (WBRT,50- 50.4 Gy; 1.8-2 Gy per fraction) were included in this study. All patients underwent a retrospective follow-up regarding acute and late side effects. Toxicities were documented using the common toxicity criteria (CTC 4.0 of the European Organization for Research and Treatment of Cancer). Results: The IOERT was well tolerated and the cosmetic results were good. As a side effect there were five patients with seroma. Two patients developed a secondary wound healing. Two patients developed chronic pain in the irradiated breast. Ten patients developed a grade 2 fibrosis. The remaining patients did not develop any grade 3 or 4 side effects. The observed toxicity rates were not influenced by age, tubus size, electron energy or systemic therapy. 80 patients had a follow up longer than 5 years. Three of them developed distant metastasis and one patient died. Conclusions: After IOERT of the breast using electrons we did not find any unexpected acute and late toxicity rates.