Intraoperative open-cavity implant for APBI using HDR multicatheter brachytherapy for Japanese patients with breast cancer and their cosmetic outcomes.

e11550 Background: The efficacy of an accelerated partial breast irradiation (APBI) has been investigated compared with whole-breast irradiation (WBI). APBI starting just after surgery might give more benefit by intra-operative insertion of catheters. Although balloon catheter-based APBI is available in the US, it would not be adapted for Japanese women with small breast. When the applicators are implanted during operation for the tumor, APBI can start just after surgery. The aim of this study is an assessment of the efficacy and safety of APBI using intra-operative open-cavity implant (IOCI) technique. Methods: Patients (≥40yrs) with invasive breast cancer (≤3 cm) were enrolled. Before the lumpectomy, the insertion of applicators and delivery doses were simulated with CT. After the confirmation of the free margin and negative SNs for metastasis using frozen section analysis, applicators were inserted. Dose distribution analysis, using dose-volume histograms, was achieved based on a postoperative CT. APBI...