Is There A Role of Post-Mastectomy Radiotherapy for T1-2 Breast Cancer Patients with Node-Positive Pathology who Develop Pathologic Negative Lymph Nodes after Neoadjuvant Chemotherapy and Mastectomy?

Abstract

To assess the benefit of post-mastectomy radiotherapy (PMRT) in breast cancer (BC) patients with T1-2N1M0 who developed pathologic negative lymph nodes (pN0) after underwent neoadjuvant chemotherapy (NAC) and mastectomy. Patients with T1-2 tumors and positive lymph node(s) who became pN0 after NAC and mastectomy were screened from our prospectively maintained database. The primary endpoint was recurrence-free survival (RFS), and the secondary endpoints included local recurrence-free survival (LRFS) and overall survival (OS). Propensity-score matching (PSM) was conducted for the comparison between PMRT and non-PMRT groups. Of the 142 eligible patients, 110 (77.5%) received PMRT and 32 (22.5%) did not. A median follow-up time was 72 months. Univariate analyses showed that 5-year RFS, LRFS, and OS rates were 88.7%, 94.5%, and 96.1% with PMRT and 72.4%, 90.1%, and 95.0% without PMRT, respectively, (P = 0.028; P = 0.151; P = 0.971). Multivariate analyses established PMRT as a significant prognostic factor for RFS rate (HR, 0.411; 95%CI, 0.175-0.968; P = 0.042). After a PSM analysis of 96 patients (64 in the PMRT group vs. 32 in the non-PMRT group), PMRT remained significant with improved RFS in univariate and multivariate analyses (with 5-year RFS rates of 90.1% vs. 72.7%, P = 0.016; HR, 0.321, 95%CI, 0.114-0.904, P = 0.031). In the subgroup of 48 (33.8%) patients with pathologic complete response (pCR) after NAC, PMRT did not affect RFS (HR, 0.226; 95%CI, 0.034-1.500; P = 0.123). PMRT may be beneficial for the pT1-2N1M0 patients with pN0 after NAC. Patients with pCR status might consider omitting the PMRT. Prospective studies are needed to further assess the effect of PMRT in this specific patient population.