Outcomes with intraoperative radiation therapy for early-stage breast cancer.

Adjuvant radiation therapy has been associated with improved local control following breast-conserving surgery. Traditionally, treatment has been delivered with whole breast irradiation over 3-6 weeks or partial breast irradiation over 1-3 weeks. However, intraoperative radiation therapy (IORT) has emerged as a technique that delivers a single dose of radiotherapy at the time of surgery for early-stage breast cancers. We report initial outcomes and acute toxicities with intraoperative radiation from a single institution. Patients with DCIS or Stage I-II breast cancer who underwent lumpectomy and sentinel lymph node biopsy (nodal sampling excluded in some cases) were included. All patients in this analysis were treated with IORT as at the time of surgery, 20 Gy in 1 fraction with 50 kV x-ray. Patients were treated at a single institution between 2011 and 2019. Follow-up was per standard institutional protocol. Two hundred and one patients were included in the analysis, with a median follow-up of 23 months (range: 0-73 months). Median age was 71 years old. Overall, 4 (2.0%) patients had DCIS, 186 (92.5%) patients had Stage 1 disease, and 11 patients had (5.5%) Stage 2 disease. All patients were estrogen receptor-positive, 175 (87.9%) progesterone receptor-positive, and 1 (0.5%) HER2 amplified. The crude rate of local recurrence was 2.0% (n = 4) and distant metastasis rate was 0.5% (n = 1). The rate of arm lymphedema was 0.5% (n = 1) and chronic telangiectasia rate was 1.1% (n = 2). Intraoperative radiation therapy, in a cohort of low-risk patients, demonstrated low rates of recurrence and reproducibility in a multi-disciplinary setting. Further follow-up, analysis of patient satisfaction and cosmesis, and comparison to whole breast irradiation and partial breast techniques is necessary in order to further validate these findings.