Breast conserving surgery with intraoperative electron beam radiation therapy for low‐risk breast cancer: Five‐year follow‐up of 306 patients

Abstract

AbstractRecent studies have reported a higher than expected risk of ipsilateral breast tumor recurrence (IBTR) after breast conserving surgery (BCS) and a single dose of electron beam intra‐operative radiotherapy (IORT). This finding was the rationale to perform a retrospective single center cohort study evaluating the oncologic results of consecutive patients treated with BCS and IORT. Women were eligible if they had clinical low‐risk (N0, ≤2 cm unifocal, Bloom and Richardson grade 1–2), estrogen receptor‐positive and human‐epidermal‐growth‐factor‐receptor‐2‐negative breast cancer. Prior to BCS, pN0 status was determined by sentinel lymph node biopsy. Data on oncologic follow‐up were analyzed. Between 2012 and 2019, 306 consecutive patients were treated and analyzed, with a median age of 67 (50–86) years at diagnosis. Median follow‐up was 60 (8–120) months. Five‐year cumulative risk of IBTR was 13.4% (95% confidence interval [CI] 9.4–17.4). True in field recurrence was present in 3.9% of the patients. In 4.6% of the patients, the IBRT was classified as a local recurrence due to seeding of tumor cells in the cutis or subcutis most likely related to percutaneous biopsy. In 2.9% of the patients, the IBRT was a new outfield primary tumor. Three patients had a regional lymph node recurrence and two had distant metastases as first event. One breast cancer‐related death was observed. Estimated 5‐year overall survival was 89.8% (95% CI 86.0–93.6). In conclusion, although some of IBTR cases could have been prevented by adaptations in biopsy techniques and patient selection, BCS followed by IORT was associated with a substantial risk of IBTR.