Up to 5 years outcomes following intraoperative radiotherapy for early breast cancer

Breast conserving surgery (BCS) and adjuvant whole breast radiation therapy (WBRT) is the standard of care for early breast cancer (1). American societies recommend omission of WBRT in women older than 70 years old (yo) with stage I, ER + breast cancer who plan to receive hormone therapy (2). Long-term prospective studies are still ongoing. Classical WBRT is a long treatment [usually 50 Gray (Gy) in daily fractions for 5 consecutive weeks with an external beam boost of 10 to the tumor bed] and has acute side effects and long-term toxicities. An ipsilateral breast tumor recurrence occurs most often (85%) in the tumor bed (within 2 cm of lumpectomy) (3). Furthermore, accelerated partial-breast irradiation (APBI) is a technique that can decrease treatment time and give a better quality of life by potential reduction in treatment toxicity. Hence, the European and American Societies for Radiation Oncology made recommendations for selected patients for APBI after breast-conserving surgery (4,5). For the European Society, APBI can be proposed if women are over 50 yo with a tumor (size under 3 cm), whereas for the American Society APBI can be proposed for women over 60 yo with a tumor size under 2 cm. According to both Societies, it is necessary to have a favorable histology profile: verified invasive-ductal breast cancer, Scarf Bloom Richardson (SBR) grade ≤2, Erb2-negative, hormone receptor-positive, node-negative. Multiple techniques can be used for APBI, including accelerator with or without intensity modulated radiotherapy (6), interstitial brachytherapy (7,8), mammosite (9,10) and intra-operative radiotherapy (IORT) with either electrons or low dose X-rays (11,12). These techniques have large differences in dose rate and dose distribution and are not strictly comparable. Therefore, we will report our results with IORT only with Intrabeam device