RESUMEN
PURPOSE: To compare the effect of intraoperative radiotherapy (IORT) and no radiotherapy in early stage low-risk breast cancer patients undergoing breast-conserving surgery. METHODS: According to the criteria recommended by ASTRO for patients eligible for IORT, we retrospectively selected women with early stage low-risk breast cancer who underwent breast-conserving surgery from 2010 to 2019 from the SEER database. Propensity score matching was used to balance the differences in baseline characteristics. The Kaplan-Meier method was used to calculate the overall survival (OS) and breast cancer-specific survival (BCSS) of patients, and the log-rank test was used to compare the differences. RESULTS: A total of 20,245 patients were included in the analysis, including 1738 in the IORT group and 18,507 in the no radiotherapy group, with a median follow-up of 41 months. Before matching, the 5-year OS rates of the IORT group and the no radiotherapy group were 95.5% and 85.7% (p < 0.001), respectively, and the 5-year BCSS rates of the two groups were 99.6% and 98.3% (p < 0.001), respectively. After matching, the 5-year OS rates were 95.6% and 90.3% (p < 0.001) in the IORT group and the no radiotherapy group, respectively, and the 5-year BCSS rates were 99.5% and 99.1% (p = 0.028), respectively. Cox multivariate analysis of the original data showed that radiotherapy was an independent prognostic factor for both OS and BCSS (p < 0.05). CONCLUSIONS: For patients aged 50 years or older with early stage low-risk breast cancer, IORT may be a better option, with improved BCSS compared to the elimination of radiotherapy. The study could not draw conclusions on OS, because underlying diseases may be unevenly distributed between the two groups.