Background: The role of regional nodal irradiation (RNI) in patients with cN1 breast cancer following neoadjuvant treatment (NAT) is still controversial. The Neo-Bioscore staging system has shown promising prospect in assessing individual prognosis after NAT, and we sought to evaluate the role of Neo-Bioscore in guiding RNI following NAT.
Methods: Medical records of 163 women with cN1 and ypN0-1 disease treated with NAT between 2009 and 2014 were retrospectively reviewed and a Neo-Bioscore was assigned to each patient. Survivals were calculated using the Kaplan-Meier method and compared with the log-rank test. Multivariate analysis was used to identify independent predictors by using Cox proportional hazards models.
Results: The median follow-up after surgery was 59.4 months. Of all 163 patients, 119 received RNI. At surgery, 36 patients (22.1%) had pathological complete response (pCR), while 89 patients (54.6%) achieved ypN0. In the whole cohort, RNI significantly improved distant metastasis-free survival (DMFS) on multivariable analysis. In the subgroup of patients with a Neo-Bioscore of 1-3, RNI significantly improved the 5-year DMFS rate of 97.0% versus 76.9% (p = 0.002), 5-year regional node recurrence-free survival rate of 95.5% versus 76.9% (p = 0.007), and 5-year overall survival rate of 100% versus 89.2% (p = 0.005). No significant difference in outcomes was found between the RNI and non-RNI groups in patients with a score of 4-6.
Conclusions: In patients with cN1 and ypN0-1, RNI was found to significantly improve DMFS following NAT. Patients with a Neo-Bioscore of 1-3 are more likely to benefit from RNI, however a large prospective study is needed to confirm this finding.