Long-term Outcomes of Intraoperative Radiotherapy For Early-stage Breast Cancer in China: A Multicenter Real-World Study

Background: To assess the efficacy, safety, and cosmetic effects of breast-conserving surgery (BCS) combined with intraoperative radiotherapy (IORT) in Chinese people. Methods: : A retrospective analysis was performed on 451 patients who received IORT at four hospitals in China. IORT was delivered directly to the mammary gland before and after surgery. The primary endpoint was ipsilateral breast tumor recurrence (IBTR). The secondary endpoints were locoregional recurrence (LRR), overall survival (OS), disease-free survival (DFS), IORT-related toxicities, and cosmetic outcomes. Results: : The median follow-up was 5.4 years (with a range of 1.0 to 11.9 years). The overall IBTR was 1.5%, LRR was 2.8%, and the OS rate and DFS rate were 96.2% and 99.1%, respectively. Only one (0.2%) breast cancer-related death was recorded. The cancer-related distant metastasis rate was 0.6%. There was no intraoperative or postoperative radiation-related acute hematological toxicity or other complications. Overall, 74.3% of patients graded the cosmetic effect as excellent or good. The LRR for pre-excision IORT was 3.0%, whereas that of post-excision IORT was 2.8% (pre-IORT vs. post-IORT, p=0.772). Distant metastases rate was 2.3% for pre-IORT and 1.8% for post-IORT (pre-IORT vs. post-IORT, p=0.692). The cancer-related death rate was 0.7% for pre-IORT and 0.0% for post-IORT (pre-IORT vs. post-IORT, p=0.899). The DFS rate was 94.7% in the pre-IORT group and 95.3% in the post-IORT group. (p=0.672). The LRR was 2.4%, whereas the OS rate was 99.5% after adjusting for the age of patients according to the recommended criteria by the American Society of Therapeutic Radiation Oncology (ASTRO), and the DFS rate was 98.1%. Conclusions: : IORT significantly reduced the treatment time while preserving a high degree of locoregional control and cosmetic effects.