Abstract PS5-04-13: Intraoperative Radiotherapy in Early-Stage Breast Cancer:Long-Term Survival and Real-World Outcomes from Community Hospitals in Baltimore

Abstract Background: Breast-conserving surgery followed by whole-breast radiotherapy (WBRT) is the standard of care for early-stage breast cancer, significantly reducing the risk of local recurrence. However, WBRT requires multiple treatment sessions over several weeks, imposing logistical, financial, and compliance burdens that can particularly impact socioeconomically disadvantaged populations. Intraoperative radiotherapy (IORT), which delivers a single fraction of radiation during surgery, has been proposed as an alternative that may improve treatment adherence and reduce toxicity. While randomized trials have demonstrated non-inferiority in selected patients, real-world data on long-term oncologic outcomes in community hospital settings remain limited. This study evaluates overall survival (OS) and progression-free survival (PFS) in patients treated with IORT at MedStar community hospitals in Baltimore. Methods: In this prospective cohort study, patients with early-stage breast cancer who underwent breast-conserving surgery with IORT at four MedStar community hospitals in Baltimore between 2013 and 2019 were included. Clinical outcomes were assessed through medical records, imaging, and follow-up visits. OS and PFS at 5 years were estimated using Kaplan-Meier survival analysis, and recurrence rates were determined through clinical and radiologic evaluations. Results: A total of 115 patients were initially identified; 10 were excluded due to loss to follow-up (n=2), undocumented date of death (n=5), or receipt of adjuvant WBRT (n=3), leaving 105 patients for the final analysis. The median age was 65 years (range, 45-82), with most patients having hormone receptor-positive, HER2-negative tumors, and surgical tumor sizes ranging from 0.4 to 3.7 cm. The 5-year OS was 88%, and the 5-year PFS was 87%, demonstrating durable local disease control. Most recurrences occurred within the first five years, consistent with prior IORT studies. No severe late toxicities or unexpected adverse events were reported. Conclusions: IORT demonstrated comparable long-term OS and PFS to historical WBRT data while reducing treatment duration and eliminating the need for prolonged hospital visits. These results align with previous IORT trials, including TARGIT-A and ELIOT, which reported similar overall survival outcomes, supporting the efficacy of IORT in early-stage breast cancer. This study supports the feasibility of implementing IORT in community hospital settings, where access to prolonged radiation therapy can be challenging, and highlights its potential to improve accessibility and mitigate disparities in radiotherapy completion for socioeconomically disadvantaged populations. Further studies with larger cohorts and longer follow-up are warranted to refine patient selection and optimize treatment protocols for broader clinical application. Citation Format: A. OROSCO TTAMINA, P. Fowler, M. Farha. Intraoperative Radiotherapy in Early-Stage Breast Cancer:Long-Term Survival and Real-World Outcomes from Community Hospitals in Baltimore [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-04-13.