ABSTRACT
Objective:To compare the survival and prognostic factors of intraoperative radiotherapy (IORT) and postoperative radiotherapy (PORT) in female patients, aged≥50 years, diagnosed with node-negative breast cancer (≤ 3 cm in size).Methods:Clinical data of eligible early breast cancer patients between 2010 and 2015 were obtained from the SEER database. Patients were divided into the IORT and PORT groups according to the radiotherapy record and propensity score matching (PSM) was subsequently conducted. Kaplan-Meier curve was used to evaluate the overall survival (OS) and breast cancer-specific survival (BCSS) between two groups and Cox proportional hazard regression analysis was used to explore the risk factors of clinical prognosis.Results:7 068 patients were included after PSM. The median follow-up time was 32.0 months. The 5-year OS rates in the IORT and PORT groups were 96.8% and 93.8%, respectively. Univariate Cox analysis showed that radiotherapy, age, histological grade, T stage, estrogen receptor (ER) status and progesterone receptor (PR) status were the independent risk factors for OS, and histological grade, T stage, ER status, PR status and chemotherapy were the independent risk factors for BCSS. Multivariate Cox regression analysis demonstrated that patients who received IORT had better OS than PORT counterparts ( P=0.020). Besides, patients aged≥60 years obtained worse OS than those aged<60 years ( P=0.003). Patients with T 2 stage or ER-negative tumors had worse OS than those with T 1 stage tumors ( P<0.001) or ER-positive tumors ( P=0.001). Patients with grade Ⅲ-Ⅳ tumors achieved worse BCSS ( P=0.004). Subgroup analysis showed that IORT yielded better OS for elderly patients (≥60 years), grade Ⅲ-Ⅳ tumors, infiltrating duct carcinoma, T 2 stage tumors, ER-positive tumors, PR-positive tumors and patients without chemotherapy. Conclusions:IORT may bring benefit for highly selected patients with low risk of recurrence, which is not inferior to PORT in terms of short-term survival. Prospective studies with longer follow-up time are needed to confirm the findings.