Abstract P3-12-08: The role of neo-bioscore staging system in guiding the optimal strategies for regional nodes irradiation following primary systemic treatment in breast cancer patients with cN1 and ypN0-1

Purpose: Following primary systemic treatment (PST), the optimal strategies for regional nodal irradiation (RNI) are currently under active investigation, especially in patients with pretreatment cN1 and posttreatment ypN0-1. The Neo-Bioscore staging system has showed promising prospect in assessing prognosis after PST. In this analysis, we evaluate the role of Neo-Bioscore staging system in guiding RNI following PST in patients with cN1 and ypN0-1. Methods and Materials: Continuous women with cN1 pretreatment and who received PST with ypN0 or ypN1 posttreatment between 2009 and 2014 were retrospectively reviewed. According to the report by Mittendorf et al, the Neo-Bioscore staging system is on the basis of pretreatment clinical stage, posttreatment pathologic stage, estrogen receptor (ER) status, HER2 status and grade stage, and assigned and summed points for each factor as shown in. A pathologic complete response (pCR) was defined as no invasive disease in the breast or regional lymph nodes after surgery. The curves for survival were generated using the Kaplan-Meier method and compared using the Log-rank test. Results: One hundred and sixty-three patients were enrolled in this study, of them 18 patients received breast conserving surgery. Of the 163 patients, 119 (73%) received RNI. At surgery, 36 patients (22.1%) achieved pCR, while 89 patients (54.6%) achieved ypN0. The median follow-up was 59.4 months (rang: 16-106). In the whole cohort, RNI was associated with non-significant improved outcomes, with a 5-year locoregional recurrence free survival (LRRFS) rate of 98.6% vs. 95.7% (P=0.393), a regional recurrence free survival (RRFS) rate of 98% vs. 97.7% (P=0.865), a 5-year distant metastasis free survival (DMFS) rate of 91.6% vs. 83.4% (P=0.052), a 5-year any first recurrence free survival (RFS) rate of 90.9% vs. 87.4% (P=0.43), and a 5-year overall survival (OS) rate of 98% vs. 91.9% (P=0.097) in the RNI and non-RNI group, respectively. In the subgroup of patients with Neo-Bioscore score of 1 to 3, RNI significantly increased the 5-year DMFS rate of 97% vs. 76.9% (P=0.002), 5-year RFS rate of 95.5% vs. 76.9% (P=0.007) and 5-year OS rate of 100% vs. 89.2% (P=0.005). However, no significant difference in outcomes was found between RNI and non-RNI group in patients with Neo-Bioscore score of 4 to 6. Among patients who not achieved pCR and those with ypN1, RNI significantly increased DMFS (both P Conclusions: Not all patients with cN1 and ypN0-1 could significantly benefit from RNI following PST, those with low Neo-Bioscore score were likely to benefit more. Citation Format: Cao L, Chen J-Y. The role of neo-bioscore staging system in guiding the optimal strategies for regional nodes irradiation following primary systemic treatment in breast cancer patients with cN1 and ypN0-1 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-12-08.