Resumen de Intraoperative radiotherapy versus no radiotherapy for early stage low-risk breast cancer patients undergoing breast-conserving surgery: a propensity score matching study based on the SEER database

Yin Mi, Xiaoxiao Zuo, Qinchen Cao, Juanjuan He, Xin Sui, Jing Li, Kang Cui, Xiaoxu Ma, Nan Zhang, Yonggang Shi

• 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.