The Impact of Postmastectomy and Regional Nodal Radiation after Neoadjuvant Chemotherapy for Clinically Lymph Node Positive Breast Cancer: A National Cancer Database (NCDB) Analysis
Menée à partir des données du registre national américain des cancers portant sur 15 315 patientes atteintes d'un cancer du sein de stade cT1-3 cN1 M0 et ayant reçu une chimiothérapie néoadjuvante, cette étude évalue, du point de vue de la survie globale, l'intérêt d'une radiothérapie après mastectomie et d'une irradiation des ganglions régionaux après traitement chirurgical conservateur
Background : Following neoadjuvant chemotherapy (NAC), the optimal strategies for postmastectomy radiotherapy (PMRT) and regional nodal irradiation (RNI) after breast-conserving surgery (BCS) are controversial. In this analysis, we evaluate the impact of these radiotherapy approaches for women with clinically node-positive breast cancer treated with NAC in the National Cancer Database (NCDB). Patients and Methods : Women with cT1-3 cN1 M0 breast cancer treated with NAC were divided into four cohorts by surgery (Mastectomy [Mast] vs BCS) and pathologic nodal status (ypN0 vs ypN+). Overall survival (OS) was estimated using the Kaplan-Meier method and radiotherapy approaches were analyzed using the logrank test, multivariate Cox models, and propensity score-matched analyses (PSM). Results : From 2003-2011, 15315 cases were identified including 3040 Mast-ypN0, 7243 Mast-ypN+, 2070 BCS-ypN0, and 2962 BCS-ypN+ patients. On univariate analysis, PMRT was associated with improved OS for both Mast-ypN0 (p=0.019) and Mast-ypN+ (p<0.001) patients. On multivariate analyses adjusted for factors including age, comorbidity score, cT stage, in-breast pathologic complete response, axillary surgery, ypN stage, estrogen receptor status and hormone therapy, PMRT remained independently associated with improved OS among Mast-ypN0 (HR 0.729, CI 0.566-0.939, p=0.015) and Mast-ypN+ patients (HR 0.772, CI 0.689-0.866, p<0.001). No differences in OS were observed with the addition of RNI to breast radiotherapy for BCS-ypN0 or BCS-ypN+ patients. PSMs demonstrated identical patterns of significance. On subset analysis, OS was improved with PMRT in each pathologic nodal subgroup (ypN0, ypN1, and ypN2-3) (all p<0.05). Conclusions : In the largest reported analysis of radiotherapy for cN1 patients treated with NAC, PMRT was associated with improved OS for all pathologic nodal subgroups. No OS differences were observed with the addition of RNI to breast radiotherapy.