Abstract P3-12-11: One-year follow-up results of a multi-center trial of intra-operative radiation therapy using electronic brachytherapy at the time of breast conservation surgery for early stage breast cancer

Objectives: To describe observations of one-year follow-up of subjects treated on a multi-center, non-randomized study with a single fraction of intra-operative radiation therapy (IORT) using the Xoft® Axxent® Electronic Brachytherapy System® (eBx®) immediately following surgical resection of early stage breast cancer. Methods: Two-hundred forty three (243) subjects were treated at seventeen (17) US hospitals. Upon meeting the inclusion/exclusion criteria, patients underwent partial mastectomy, placement of a balloon applicator suitable to the surgical bed in the lumpectomy cavity and inflated with saline (30 – 75 cc). The skin was temporarily closed over the balloon and ultrasound examination performed to confirm that the balloon surface-to-skin distance was > 1.0 cm. A single fraction of intra-operative radiation therapy was delivered to the lumpectomy cavity using the Xoft System. The prescribed dose was 20 Gy at the balloon applicator surface, and the mean treatment time was 10.2 minutes. After treatment, the balloon was deflated and removed, and skin sutured. Results: Two-hundred forty two (242) subjects received the prescribed dose of 20 Gy; one subject received 21 Gy. Eighteen (18) subjects were removed from the primary analysis post-IORT due to positive surgical margins (N=2), positive sentinel lymph nodes (N=13), or balloon surface-to-skin distance Conclusions: IORT using the Xoft System as part of the conservative treatment of breast cancer is safe, with low morbidity. Early results from this multi-center trial demonstrate this short, convenient course of radiation therapy for select patients with early stage breast cancer has excellent-to-good cosmetic results and a low rate of low-grade adverse events. Citation Format: Syed AMN, Chang H, Schwartzberg BS, Bremner AK, Lopez-Penalver C, Coomer C, Boylan S, Chakravarthy A, Vito CA, Bhatnagar A, Proulx GM, Dooley WC, Davis M, Golder SL, Ivanov O, Fernandez K, Rahman S. One-year follow-up results of a multi-center trial of intra-operative radiation therapy using electronic brachytherapy at the time of breast conservation surgery for early stage breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-11.