Long-Term Outcomes of an International Cooperative Study of Intraoperative Radiotherapy Upfront Boost With Low Energy X-Rays in Breast Cancer.

Purpose: The purpose of this study was to assess the effectivity of upfront kilovoltage intraoperative radiotherapy (IORT) as a boost in high-risk early-stage breast cancer patients from an international pooled cohort.
Materials/methods: Patients from four centers in three different countries were retrospectively screened. Those with a minimum 1-year follow-up were included. Cumulative local (LR), regional (RR), and distant metastasis rates (DM) were analyzed. Additionally, the estimated overall survival (OS) was assessed. The Cox regression analysis was performed to identify failure predicting factors.
Results: A total of 653 patients from centers in Peru, Spain, and Germany were included. The median follow-up was 55 (12-180) months, and age was 58 (27-86) years. Clinical tumor (T) staging was T1 65.85%, T2 30.17%, and T3 3.98%. Positive margins were found in 7.9% and in-situ component in 20.06%. The median IORT dose was 20 (6-20). The median time from IORT to EBRT was 74.5 (13-364) days. An overall 3.4% (n = 22) of patients developed local recurrence at some point during follow-up. The 12-, 60-, and 120-month cumulative LR were 0.3%, 2.3%, and 7.9%, respectively. After multivariate analysis, only age <50 remained to be a significant prognostic factor for local recurrence (HR 0.19, 95% CI 0.08-0.47; p < 0.05). The 10-year estimated OS was 81.2%.
Conclusion: Upfront boost with IORT yields similar local control outcomes to those EBRT-based reports. Results from prospective trials, regarding toxicity, cosmesis, and effectivity are awaited to confirm these findings.
Competing Interests: GS: personal fees and travel costs from Carl Zeiss Meditec AG, personal fees from Roche Pharma AG, personal fees from MedWave Clinical Trials, travel costs from Guerbet SA, not related to this work. FW: reports personal fees from Celgene GmbH, fees Roche Pharma AG, fees Eli Lilly and Company, fees from Ipsen Pharma GmbH and grants and other from Carl Zeiss Meditec AG and Elekta AB, patent by Carl Zeiss Meditec AG, not related to this work, outside the submitted work. FG: grants and personal fees from Carl Zeiss Meditec AG, personal fees from Roche Pharma AG, grants and personal fees from Elekta AB, grants and personal fees from NOXXON Pharma AG, grants and personal fees from Bristol-Myers Squibb, grants and personal fees from MSD Sharp and Dome GmbH, grants and personal fees from AstraZeneca GmbH, non-financial support from ONCARE GmbH, non-financial support from OPASCA GmbH, outside the submitted work. GS: personal fees and travel costs from Carl Zeiss Meditec AG, not related to this work. ES: grants from the Ministry for Science and Arts and others from Carl Zeiss Meditec, outside of the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2022 Sarria, Ramos, Palacios, Del Castillo, Castro, Calvo, Cotrina, Heredia, Galarreta, Fuentes-Rivera, Avalos, Martinez, Colqui, Ziegler, Schmeel, Pinillos, Wenz, Giordano, Sarria and Sperk.)