The Role of Postmastectomy Radiation Therapy After Neoadjuvant Chemotherapy in Clinical Stage II-III Breast Cancer Patients With pN0: A Multicenter, Retrospective Study (KROG 12-05)

Abstract

The purpose of this study was to investigate the role of postmastectomy radiation therapy (PMRT) after neoadjuvant chemotherapy (NAC) in clinical stage II-III breast cancer patients with pN0. We retrospectively identified 417 clinical stage II-III breast cancer patients who achieved an ypN0 at surgery after receiving NAC between 1998 and 2009. Of these, 151 patients underwent mastectomy after NAC. The effect of PMRT on disease-free survival (DFS), locoregional recurrence-free survival (LRRFS), and overall survival (OS) was evaluated by multivariate analysis including known prognostic factors using the Kaplan-Meier method and compared using the log-rank test and Cox proportional regression analysis. Of the 151 patients who underwent mastectomy, 105 (69.5%) received PMRT and 46 patients (30.5%) did not. At a median follow-up of 59 months, 5 patients (3.3%) developed LRR (8 sites of recurrence) and 14 patients (9.3%) developed distant metastasis. The 5-year DFS, LRRFS, and OS rates were 91.2, 98.1, and 93.3% with PMRT and 83.0%, 92.3%, and 89.9% without PMRT, respectively (all P values not significant). By univariate analysis, only age (≤40 vs >40 years) was significantly associated with decreased DFS (P=.027). By multivariate analysis, age (≤40 vs >40 years) and pathologic T stage (0-is vs 1 vs 2-4) were significant prognostic factors affecting DFS (hazard ratio [HR] 0.353, 95% confidence interval [CI] 0.135-0.928, P=.035; HR 2.223, 95% CI 1.074-4.604, P=.031, respectively). PMRT showed no correlation with a difference in DFS, LRRFS, or OS by multivariate analysis. PMRT might not be necessary for pN0 patients after NAC, regardless of clinical stage. Prospective randomized clinical trial data are needed to assess whether PMRT can be safely omitted in pN0 patients after NAC and mastectomy for clinical stage II-III breast cancer.