Int J Cancer Manag. 2019 August; 12(8):e94547. Published online 2019 August 24. doi: 10.5812/ijcm.94547. Research Article Comparing the Outcome of Boost Dose of Intraoperative Radiotherapy with Electron (IOERT) and Low-kV X-Ray (IOXRT) and External Beam Radiotherapy (EBRT) in Breast Cancer After Neoadjuvant Chemotherapy Nazi Moini 1 , Nahid Nafissi 2 , Ebrahim Babaee 3 , Hamidreza Mirzaei 1 and Mohammad Esmaeil Akbari 1, * 1 Cancer Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2 Cancer Research Center, Iran University of Medical Science, Tehran, Iran 3 Preventive Medicine and Public Health Research Center, Iran University of Medical Science, Tehran, Iran * Corresponding author: Cancer Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Email: profmeakbari@gmail.com Received 2019 May 27; Revised 2019 June 09; Accepted 2019 July 29. Abstract Background: In the large breast tumors or locally-advanced breast cancers, breast conserving surgery (BCS) after neoadjuvant chemotherapy (NACT) had an acceptable local control, but greater risk of recurrence. Adding boost dose radiation to whole breast radiotherapy is involved with a reduced risk of recurrence. Boost radiotherapy can be delivered in 3 methods, including (1) external beam radiotherapy (EBRT), (2) intraoperative radiotherapy with electron (IOERT), and (3) intraoperative radiotherapy with low-kV X-ray (IOXRT). Objectives: This study compared the outcomes of these 3 methods with each other. Methods: Within 60 months, 217 unselected breast cancer patients in Cancer Research Center of Shahid Beheshti were under treat- ment with BCS after NACT. They received boost dose radiation in 3 groups; 115 patients in the EBRT group, 39 patients IOXRT group, and 63 patients in the IOERT group. All of them received WBRT after surgery. Results: The patients had large tumors or stage 3 breast cancer. Local recurrences were 1 (2.5%) in IOXRT, 2 (3.2%) in IOERT, and 1 (0.9%) in EBRT groups. Systemic recurrences were 4 (10.3%) in IOXRT, 10 (15.9%) in IOERT, and 16 (13.9%) in EBRT groups. Deaths were 3 (7.7%) in IOXRT, 2 (3.2%) in IOERT, and 10 (6.9%) in EBRT groups. Patients with any events were 4 (10.3%) in IOXRT, 11 (17.5%) in IOERT, and 33 (15.2%) in the EBRT group. Death due to distant metastases was lower in IOERT group, but it was not significant. No significant difference was observed in disease-free survival (DFS) among 3 groups. IOXRT group had non-significant, lower events, and better DFS. Especially, in non-PCR (non-pathologic complete response) patients, multivariate COX analysis showed better outcome (DFS) in IOXRT group (HR = 0.50), although it was not significant (P = 0.53). Conclusions: Intraoperative radiotherapy (IORT or IOXRT) as tumor bed boost during BCS after NACT had at least non-inferiority compared with EBRT. In non-PCR patient, IOXRT group had non-significant better outcomes (DFS). Keywords: Intraoperative Radiotherapy, IORT, IOERT, IOXRT, Neoadjuvant Chemotherapy, DFS 1. Background Preoperative chemotherapy (neoadjuvant) describes the management of chemotherapy before surgery. The ini- tial indication of neoadjuvant therapy is traditionally for facilitating breast surgery. Patients requesting breast con- servation, who are not candidates of this approach after diagnosis, might expect overall breast conservation rates of 72.3% (OR = 1.7, 95% CI = 1.6 - 1.8) (1, 2). No difference has been observed in disease-free survival (DFS) or OS in multiple neoadjuvant versus adjuvant therapy trials (3-5). Several studies in patients with large or local advanced breast cancer (LABC) indicated appropriate local control in breast conserving surgery (BCS) (3, 4, 6). Nevertheless, the other large randomized trials show a non-significant rise in breast recurrence in the conservation group compared with mastectomy group (4, 5). The patients achieving a pathologic complete response (PCR) defined as ypT0/ypN0 probably experience more survival benefits in comparison with those who cannot achieve a PCR (7). Adding a radiation therapy “boost” or an additional Copyright © 2019, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.