ORIGINAL ARTICLE – BREAST ONCOLOGY Local Failure After Accelerated Partial Breast Irradiation with Intraoperative Radiotherapy with Electrons: An Insight into Management and Outcome from an Italian Multicentric Study Maria Cristina Leonardi, MD 1 , Luigi Tomio, MD 2 , Davide Radice, MSc 3 , Silvia Takanen, MD 4 , Elisabetta Bonzano, MD 5 , Marina Alessandro, MD 6 , Antonella Ciabattoni, MD 7 , Giovanni Battista Ivaldi, MD 8 , Vincenzo Bagnardi, PhD 9 , Ombretta Alessandro, MD 1,10 , Claudia Maria Francia, MD 1 , Cristiana Fodor, MSc 1 , Eleonora Miglietta, MSc 1 , Paolo Veronesi, MD 10,11 , Viviana Enrica Galimberti, MD 11 , Roberto Orecchia, MD 12 , Luca Tagliaferri, MD 13 , Cristiana Vidali, MD 14 , Mariangela Massaccesi, MD 13 , Marina Guenzi, MD 5 , Barbara Alicja Jereczek-Fossa, MD, PhD 1,10 on behalf of the Study Groups ‘‘Brachytherapy, Interventional Radiotherapy and Intraoperative Radiotherapy’’ and ‘‘Reirradiation’’ of the Italian Radiotherapy and Clinical Oncology Society (AIRO) 1 Division of Radiation Oncology, European Institute of Oncology, IEO, IRCCS, Milan, Italy; 2 Radiotherapy Unit, Santa Chiara Hospital, Trento, Italy; 3 Division of Epidemiology and Biostatistics, European Institute of Oncology, IEO, IRCCS, Milan, Italy; 4 Radiotherapy Unit, Papa Giovanni XXIII Hospital, Bergamo, Italy; 5 Department of Radiation Oncology, IRCCS Policlinico San Martino and University, Genoa, Italy; 6 Radiotherapy Division, Citta ` di Castello Hospital, Citta ` di Castello, Italy; 7 Department of Radiotherapy, San Filippo Neri Hospital, Rome, Italy; 8 Department of Radiotherapy, Istituti Clinici Scientifici Maugeri¸IRCCS, Pavia, Italy; 9 Department of Statistics and Quantitative Methods, University of Milan- Bicocca, Milan, Italy; 10 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy; 11 Division of Breast Surgery, European Institute of Oncology, IEO, IRCCS, Milan, Italy; 12 Scientific Directorate, European Institute of Oncology, IEO, IRCCS, Milan, Italy; 13 UOC Radioterapia, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy; 14 Department of Radiotherapy, Azienda Sanitaria Universitaria Integrata di Trieste, Trieste, Italy ABSTRACT Background. The aim of this work is to evaluate pattern of care and clinical outcome in a large series of patients with in-breast recurrence (IBR), after quadrantectomy and intraoperative radiation therapy with electrons (IOERT) as partial breast irradiation. Patients and Methods. Patients with IBR after IOERT, treated with salvage surgery ± adjuvant reirradiation (re- RT), were selected from a multiinstitution database. Dis- ease-free survival (DFS), overall survival (OS), cumulative incidence of second IBR, and distant metastases (DM) were estimated. Results. A total of 224/267 patients from seven institutions were included. Primary tumors received 21 Gy. Median time to first IBR was 4.3 years (range 2.6–6.1 years). Salvage mastectomy and repeat quadrantectomy were performed in 135 (60.3%) and 89 (39.7%) patients, followed by adjuvant re- RT in 21/135 (15.5%) and 63/89 (70.8%), respectively. Median follow-up after salvage treatment was 4.1 years. Overall, 5- and 8-year outcomes were as follows: cumulative incidence of second IBR: 8.4% and 14.8%; cumulative inci- dence of DM: 17.1% and 22.5%; DFS: 67.4% and 52.5%; OS: 89.3% and 74.7%. The risk of second IBR was similar in the Marina Guenzi and Barbara Alicja Jereczek-Fossa: co-last author. Electronic supplementary material The online version of this article (https://doi.org/10.1245/s10434-019-08075-3) contains supplementary material, which is available to authorized users. Ó Society of Surgical Oncology 2019 First Received: 12 August 2019 M. C. Leonardi, MD e-mail: cristina.leonardi@ieo.it L. Tomio, MD e-mail: ltomio@yahoo.it Ann Surg Oncol https://doi.org/10.1245/s10434-019-08075-3