Intraoperative radiotherapy in early breast cancer: 400 consecutive patients in one institution.

1108 Background: From 2006 we offer intraoperative radiotherapy as the only post lumpectomy breast irradiation as an alternative to the standard post-operative WBRT in low risk early breast cancer patients (age > 60, invasive ductal carcinoma < 2 cm and clinically negative axilla). Younger patients (>50) or patients with tumors up to 3.5 cm or other histologies are treated too if they are not candidate for standard local therapy. In patients found to have high risk tumor characteristics at final pathology, additional local breast therapy is considered. Methods: Intrabeam System is used administering 20 Gy at the surface of surgical cavity. Results: 400 patients were treated. Their median age was 70 years (55-90). Median clinical tumor size was 12 mm (5-30). 14.5% had mild to moderate local complications: 6.5% wound infection, 5.8% complicated seromas, 1.7% bleeding or hematoma and 0.5% small skin necrosis. 6.2% experienced major complications: 2.5% required surgical intervention, 2% had late healing (> 90 days), 1% required IV antibiotics and 0.7% had grade III RTOG fibrosis. Median pathologic size was 14 mm (1-40). Pathologic free margins > 1mm were obtained in 98.8% of patients. 15.5 % were found to have axillary l-nodes involved (11% one node only), 12% of patients had adverse unexpected breast pathologic findings (7.5% EDCIS or LVI) and 11% had additional local therapy, most of them WBRT. Median follow up is 30 months (1-76) in the whole group and 43 months (3-76) in the first 200 patients treated. Seven ipsilateral breast failures (1.7%) and one axillary recurrence were observed, all had radical local therapy. Four patients developed systemic disease (1%), one of them with simultaneous breast recurrence and one had contralateral breast cancer. Conclusions: We conclude that intraoperative radiotherapy using the Intrabeam system is feasible and may offer an alternative to whole breast RT in low risk breast cancer patients. Clinically significant local morbidity rate is low and self limiting. Longer follow up is needed to evaluate final results and late toxicity.