Abstract PS15-11: Intraoperative radiation therapy (IORT) for1200 early breast tumors

Abstract

Abstract Introduction: Two prospective randomized trials, TARGIT-A and ELIOT, have shown intraoperative radiation therapy (IORT) to be a safe alternative with a low-risk of local recurrence compared to whole breast radiation therapy following breast conserving surgery for selected low-risk patients. We report the first 1200 tumors treated with this modality at our facility.Methods: 1200 distinct breast cancers in 1169 patients (31 bilateral) were treated with breast conserving surgery and X-ray IORT, using the Xoft Accent System from June 2010 to November 2018. Patients were enrolled in an IORT registry trial and data were collected at 1 week, 1 month, 6 months, 1 year, and yearly thereafter. The primary endpoint was local recurrence.Results: To date, there have been 61 events in 54 patients: 50 ipsilateral local recurrences (14 DCIS and 36 invasive), 7 regional nodal recurrences and 4 distant recurrences. Of local recurrences, 9 were within the IORT field, 21 outside of the IORT field but within the same quadrant as the index cancer, and 20 were new cancers in different quadrants. There has been no breast cancer related deaths and 27 non-breast cancer deaths. Currently, with a median follow-up of 52 months, Kaplan Meier analysis projects 5.2 % local recurrence rate at 5 years. In the table below, the five-year probability of local recurrence is analyzed by quadrant and/or type of recurrence (all recurrences or just invasive). Using the 2017, ASTRO Categories, 520 patients (43%) were suitable for IORT, 415 (35%) were cautionary, and 265 (22%) were unsuitable for IORT after final histopathology was evaluated.Conclusion: IORT is profoundly convenient. When used as the only adjuvant breast irradiation, it eliminates approximately 15-35 outpatient visits. This has become increasingly important during the current COVID-19 pandemic. In the group of patients described here, more that 100,000 patient-hours were saved. The local, regional, and distant recurrence rates observed in this trial were slightly higher than those of the prospective randomized TARGIT-A and ELIOT Trials. This may be explained by 22% of our patients being considered unsuitable for IORT by ASTRO Criteria. The low complication rates previously reported by our group as well as the low recurrence rates reported in this study support the cautious use and continued study of X-ray IORT in women with low-risk breast cancer. Citation Format: Melinda Epstein, Melvin Silverstein, Peter Chen, Kevin Lin, Brian Kim, Sadia Khan, Lincoln Snyder, Lisa E. Guerra, Colleen Coleman. Intraoperative radiation therapy (IORT) for1200 early breast tumors [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-11.