Outcomes of Radical and Boost Dose of Intraoperative Radiotherapy with Electron and Low KV X-Ray Based on Islamic Republic Intraoperative Radiotherapy (IRIORT) Consensus and the External Beam Radiotherapy in Pure Ductal Carcinoma in Situ (DCIS) in Breast Cancer Patients

Abstract

Background: Radiotherapy plays an essential role in breast cancer treatment following breast conserving surgery even in good-risk patients with ductal carcinoma in situ (DCIS) histology. It can be delivered by many techniques, among which is intraoperative radiotherapy (IORT). In recent years, intraoperative radiation therapy has had the same outcome compared with EBRT. Objectives: We studied whether whole breast radiotherapy (WBRT) could safely be replaced by IORT and its ability to control local recurrence like EBRT in pure DCIS. Methods: We assigned 138 patients into the external beam radiotherapy (EBRT), radical, and boost groups. The patients were treated during the last 6 years in the Cancer Research Center of Shahid Beheshti University of Medical Sciences. A total of 57 patients received EBRT, 45 patients received the radical dose of radiotherapy by IORT (36 patients received intraoperative electron radiotherapy [IOeRT] and 9 patients received intraoperative X-ray radiotherapy [IOxRT]) according to the IRIORT consensus protocol, and 36 patients received the boost dose of radiotherapy by IORT (15 patients received IOeRT and 21 patients received IOxRT). The IORT and EBRT groups were compared. The primary endpoint was local recurrence and death and the secondary endpoint was the role of variables in local recurrence. Results: With the mean follow-up of 37 months for the IORT group and 40.1 months for the EBRT group, local recurrence occurred in 8.8% (5 patients), 13.9% (5 patients), and 2.2% (1 patient) of the patients in the EBRT, boost, and radical groups, respectively. Concerning the local recurrence, no significant difference was observed between the radical and EBRT groups (P = 0.058) and between the boost and EBRT groups (P = 0.12). Hazard ratios (HRs) of grade, hormone receptor (HR), tumor size, and age in disease-free survival were evaluated and none of these variables had a significant role in local recurrence. Conclusions: IORT is a good alternative for WBRT in DCIS patients because of its non-inferiority results in comparison with EBRT. Being careful about age, tumor size, biological markers, and margin status is of high importance when using IORT for DCIS.