Intraoperative electron radiotherapy in early-stage breast cancer: A report on 226 patients.

Abstract

143 Background: We report the results of a single-institution phase II trial of accelerated partial breast irradiation (APBI) using a single dose of intraoperative electron radiotherapy (IOERT) in patients with low-risk early-stage breast cancer. Methods: From July 2006 to December 2009, 226 patients suitable for BCT were enrolled in a phase II trial with IOERT as radical treatment immediately after surgical resection. All patients had biopsy-proven cancer. After the surgeon temporarily re-approximated the excision cavity, a dose of 21 Gy using IOERT was delivered to the tumor bed with a margin of 2 cm laterally. Results: No acute reactions were reported after irradiation. Three patients experienced a transient edema. In 7 others a haematoma was observed. No cases of liponecrosis were observed. With a mean follow-up of 49 months (range 31-66 months), only one case of local recurrence has been reported. The observed toxicity was considered acceptable. As to cosmetic results, at 6 months after the end of IORT, 71/226 patients (31.4.%) had a score of 2 for symmetry and contour (asymmetry exhibited by 1/3 or less of volume breast), while 19/226 (8.4%) had a score 3 (asymmetry greater than 1/3 of breast volume). These findings remained unchanged at the following examinations. No breast oedema, discoloration at site or scar prominence were observed. Conclusions: IOERT offers the advantage of an excellent delineation of the tumor bed under visual control and high sparing of normal tissue, including the skin. IOERT delivers a very high biologically dose at the time of the surgery, when residual tumor cells are more rapidly proliferating. IOERT is insensitive to chemotherapy sequencing since all of the radiation is given during the surgery. The absolute recurrence rate of 0.4% and the recurrence rate per year of 0.2% of the present study are very encouraging. APBI using a single dose of IOERT can be delivered safely in women with early, low-risk breast cancer. A longer follow-up is needed to ascertain its efficacy compared to that of the current standard treatment of whole breast irradiation.