术前分段乳腺照射(PBI)能够实现更小的靶区和减少对正常组织的剂量。我们假设对完整乳腺肿瘤实施术前立体定向消融放射治疗(SABR)，在保持低毒性和良好外观的情况下，能达到25%的病人病理完全缓解(pCR)。符合条件的病人为雌激素受体阳性，临床上无淋巴结转移的乳腺癌，MRI测量≤2cm。病人在俯卧位的MRI和CT上，接受3次9.5 Gy的SABR照射到MRI定义的肿瘤，6-8周后进行保乳手术，对肿瘤的病理反应进行评估，并根据疾病术语临床不良事件版本4.0标准对不良事件进行评估。也报告了医生对外观的评估。共有20名病人完成治疗，并且由于预先设定的停止规则，研究在完全纳入之前终止。中位随访时间为14个月。病人的中位年龄为65岁(范围54-78)，MRI测量的中位肿瘤大小为10.5mm(范围5-22)。所有病人的手术切缘都为阴性。由于淋巴结前哨阳性，有4名病人(20%)需要术后进行全乳房和腋窝放疗。没有观察到pCR，尽管百分之中位数残留肿瘤细胞密度为30%(范围10-80)，90%的病人的残留细胞密度≤50%。3名病人出现了晚期3级不良事件，包括4名接受术后放疗的病人中的2名。85%的病例外观良好，10%为一般，5%为差。我们观察到术前SABR对早期乳腺癌的pCR发生率为0%，评估时间为治疗后6-8周。pCR的进展可能需要比6-8周更长的时间。需要进一步研究来确定最佳的患者筛选、治疗方法和病理反应评估的时间。版权所有©2023 Elsevier Inc.发表。

Pre-operative delivery of partial breast irradiation (PBI) facilitates smaller target volumes and reduced dose to normal tissues. We hypothesized that pre-operative stereotactic ablative radiotherapy (SABR) delivered to intact breast tumor would achieve pathological complete response (pCR) in 25% of patients while preserving low rates of toxicity and good cosmesis.Eligible patients had hormone receptor-positive, clinically node-negative breast cancer measuring ≤2cm on magnetic resonance imaging (MRI). Patients received SABR to 28.5 Gy in three fractions of 9.5 Gy to the tumor defined on MRI and computed tomography in the prone position. Lumpectomy was performed 6-8 weeks later. Tumor pathologic response was assessed and adverse events (AEs) were rated on the Common Terminology Criteria for AEs version 4.0 scale. Physician-rated cosmesis are also reported.Twenty patients were enrolled and completed treatment; the study was terminated prior to full accrual due to pre-specified stopping rules. Median follow-up was 14 months. Median patient age was 65 years (range 54-78) and median tumor size on MRI was 10.5mm (range 5-22). All patients had negative surgical margins. Four patients (20%) required post-operative whole breast and axillary radiation due to positive sentinel lymph nodes. No pCR were observed, although the median percent residual tumor cellularity was 30% (range 10-80) and 90% had ≤50% residual cellularity. Three patients had late grade 3 AEs, including 2 of the 4 patients who received post-operative RT. Cosmesis was good in 85% of cases, fair in 10%, and poor in 5%.We observed a 0% incidence of pCR with pre-operative SABR for early-stage BrCa as evaluated 6-8 weeks following treatment. Evolution of pCR may require longer than 6-8 weeks. Patients requiring post-operative whole breast radiotherapy after pre-operative SABR may be at increased risk for high-grade soft tissue toxicity. Further studies are needed to determine optimal patient selection, treatment methodology and timing of pathologic response evaluation.Copyright © 2023. Published by Elsevier Inc.