Intraoperative Electron Radiotherapy (IOERT) as an Alternative to Standard Whole Breast Irradiation: Only for Low-Risk Subgroups?

Abstract

Background: Intraoperative radiotherapy during breast-conserving surgery is being studied as an alternative to 6 weeks of external beam radiotherapy (EBRT) for low-risk women; it can be delivered using electrons (intraoperative electron radiotherapy, IOERT) or 50-kV X-rays. Materials and Methods: We analyzed both single institutional and randomized studies involving single-fraction IOERT treatments. Rates for ipsilateral breast tumor recurrences, disease-specific survival, and overall survival were obtained. Results: IOERT had true 5-year recurrence rates of < 1.5% for ASTRO (American Society for Radiation Oncology) and ESTRO (European Society for Therapeutic Radiology and Oncology) suitable women, or for low-risk women as defined by the ELIOT trial. Women with ductal carcinoma in situ eligible for breast-conserving therapy, older women that currently receive no EBRT, and younger women with favorable biology are additional potential candidates. Conclusion: ASTRO suitable and ESTRO good women for accelerated partial breast irradiation are low-risk groups. Higher-risk women with favorable biology might also be suitable candidates for IOERT, providing the tumor biology can be determined prior to surgery. For intraoperative radiotherapy using 50-kV X-rays, follow-up was too short to assess the effectiveness of the treatment.