Intraoperative Radiation Therapy: A Large Integrated Health Care System’s Approach and Outcomes

INTRODUCTION: Intraoperative radiation therapy (IORT) may not be as effective in the community compared with clinical trials. METHODS: The authors reviewed data from the electronic health records of patients who received IORT between February 2014 and February 2020 at a single center within a large integrated health care system. The primary outcome was ipsilateral breast tumor recurrence. RESULTS: Of 5731 potentially eligible patients, 245 (4.3%) underwent IORT (mean age: 65.4 ± 0.4 years; median follow-up time: 3.5 years ± 2.2 months). According to the American Society for Radiation Oncology’s accelerated partial breast irradiation guidelines based on final pathology, 51% of patients were suitable candidates for IORT, 38.4% were cautionary, and 10.6% were unsuitable. For adjuvant therapy, 6.5% had consolidative whole breast irradiation, and 66.4% received endocrine treatment. At the median follow-up time of 3.5 years, overall ipsilateral breast tumor recurrence was 3.7%. Recurrences tended to be more frequent in patients who refused or did not complete endocrine treatment than in those who received it (7.4% vs 1.9%, p = 0.07). The complication rate was 14.7%, with seroma being the most common (8.2%). DISCUSSION: The IORT ipsilateral breast tumor recurrence rate of 3.7% confirms a higher-than-expected rate compared to randomized clinical trials, possibly due to less compliance with endocrine therapy. CONCLUSION: The authors subsequently revised their IORT protocol to require endocrine treatment as a part of the IORT treatment plan and to strongly recommend adjuvant whole breast irradiation for all patients deemed cautionary or unsuitable for IORT according to the American Society for Radiation Oncology’s accelerated partial breast irradiation guidelines.