Outcomes of Technically Optimal Intraoperative Radiation Therapy With Electrons Versus Whole-Breast External Beam Radiation in Suitable Patients With Breast Cancer.

Purpose: Intraoperative radiation therapy (IORT) with electrons is associated with higher rates of ipsilateral breast tumor recurrence in early-stage breast cancer than whole-breast external beam radiation therapy (EBRT). Although limited randomized and retrospective data suggest that this approach may suit a subset of patients, its role remains uncertain. This study aimed to compare oncological outcomes between technically optimal IORT with electrons and whole-breast EBRT in suitable patients with breast cancer. Methods and Materials: In this single-center retrospective cohort study, patients were grouped by radiation treatment: IORT with electrons or whole-breast EBRT. Endpoints included disease-free survival (DFS), local control, and breast cancer-specific survival (BCSS). Results: From January 2011 to December 2021, 204 eligible patients were reviewed (IORT, 74; EBRT, 130). The median follow-up was 5.1 years. The 5-year DFS rates were 95.61% for IORT and 98.08% for EBRT (log-rank Conclusions: IORT with electrons was associated with a modest but statistically significant reduction in 5-year DFS in appropriately selected patients compared with whole-breast EBRT, whereas BCSS remained comparable between groups. Therefore, electron-based IORT should be approached with caution and reserved for patients who prioritize treatment convenience.