Recurrence Risk Score Model for Evaluating the Impact of Postmastectomy Radiotherapy in Breast Cancer Patients with Pathologic Nodal Negative after Neoadjuvant Chemotherapy and Mastectomy

Abstract

Recurrence risk score model was established to distinguish the recurrent risk of patients with pathologic nodal negative (ypN0) after neoadjuvant chemotherapy (NACT) and mastectomy and determine the impact of postmastectomy radiotherapy (PMRT). This multicenter retrospective study reviewed 766 patients who underwent mastectomy and NACT with ypN0 from 2000 to 2014. Recurrent risk score model was assigned proportionally to the relative contribution of independent prognostic factors in the multivariate Cox model of disease-free survival (DFS). Decision tree analysis was conducted to determine two optimal cutoff points for stratification. The median follow-up time was 74 months. The 5-year locoregional control (LRC), DFS, and overall survival (OS) rates for the entire group were 96.5%, 89.1% and 95.3%, respectively. 353 (46.1%) patients received PMRT and 413 (53.9%) patients did not. Patients with PMRT have more high-risk factors, including age <40 years, clinical stage III, grade III, or ER and PR negative. Chest wall and regional nodal region were irradiated in 307 (87.0%) and chest wall only in 46 (13.0%). The median radiation dose was 50 Gy (range: 36-60 Gy) in 25 fractions (range: 15-30 fractions). There were no significant differences between the PMRT and No-PMRT groups in the LRC, DFS and OS rates. Recurrent risk score model consisted of five factors and used a range of zero to eleven scoring points: age <40 years and clinical N1 stage for one point; clinical N2, NACT ≥4 cycles, lymphovascular invasion and ypT1-2 for two points; ypT3-4 for four points. 456 (59.5%) patients scoring zero to four points, 188 (24.5%) scoring five points and 122 (15.9%) scoring six to eleven points were assigned to the low-, intermediate-, and high-risk group. LRC, DFS and OS rates in three risk groups were significantly distinct from each other (5yr-LRC: 98.6% vs. 95.5% vs. 89.8%, p < .001; 5yr-DFS: 94.4% vs. 87.4% vs. 71.5%, p < .001; 5yr-OS: 97.6% vs. 93.2% vs. 90.0%, p < .001). PMRT had no impact on the LRC, DFS and OS rates in either low-, intermediate-, or high-risk group. The recurrence risk score model can effectively distinguish patients with different recurrent risk stratification. PMRT in patients with ypN0 after NAC and mastectomy cannot improve LRC, DFS or OS. Table 1. Survival outcomes and comparison between PMRT and No-PMRT arms in different groups.