title: Predictive Value of Molecular Subtyping for Locoregional Recurrence in Early-Stage Breast Cancer with N1 without Postmastectomy Radiotherapy.
abstract: OBJECTIVE
  This study was designed to investigate the relationship between molecular subtype and locoregional recurrence (LRR) in patients with early-stage breast cancer with 1-3 positive axillary lymph nodes (ALNs) and improve the individualized indications for postmastectomy radiotherapy (PMRT).
  
  
  METHODS
  The records of 701 patients with pT1-2N1M0 breast cancer who did not undergo PMRT were retrospectively analyzed. Tumors were subclassified as follows: luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)-enriched, and basal-like subtypes. Multivariate Cox analysis was used to determine the risk of LRR associated with the different subtypes and to adjust for clinicopathologic factors.
  
  
  RESULTS
  Luminal A, luminal B, HER2-enriched, and basal-like subtypes accounted for 51.2%, 28.0%, 8.1%, and 12.7% of cases, respectively. The median follow-up duration was 67 months (range, 9-156 months). Univariate analysis revealed that, compared with the luminal A subtype, the HER2-enriched and basal-like subtypes were associated with significantly higher 5-year LRR rates (5.6% vs. 21.6% and vs.15.7% respectively; p=0.002 each), lower 5-year LRR-free survival (LRFS) rates (90.6% vs. 73.8% and 78.5%, respectively; p=0.001 each), and poorer 5-year breast cancer-specific survival (BCSS) rates (93.7% vs. 82.2% [p=0.002] and 84.9% [p=0.001], respectively). Multivariate analysis revealed that the HER2-enriched and basal-like subtypes, age ≤35 years, a medial tumor, and pT2 stage were poor prognostic factors for LRR and LRFS; furthermore, 2 to 3 positive ALNs represented an independent prognostic factor affecting LRR. The 10-year LRR rates of patients with 0, 1, 2, 3, and 4 risk factors were 1.0%, 6.9%, 14.3%, 30.4%, and 54.3%, respectively (p<0.001); the 10-year BCSS rates were 86.6%, 88.5%, 84.4%, 79.7%, and 38.8%, respectively (p<0.001).
  
  
  CONCLUSIONS
  Molecular subtyping allows for individualized evaluation of LRR risk in patients with pT1-2N1M0 breast cancer. PMRT should be recommended for patients with ≥3 LRR risk factors.
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangdong, China.; Department of Radiation Oncology, Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
authors.forename: Ge
authors.initials: G
authors.lastname: Wen
authors.affiliation: Department of Radiation Oncology, Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
authors.forename: Jin-Shan
authors.initials: JS
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangdong, China.
authors.forename: Yu-Jing
authors.initials: YJ
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangdong, China.
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Zhu
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangdong, China.
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangdong, China.
authors.forename: Xun-Xing
authors.initials: XX
authors.lastname: Guan
keywords: Breast neoplasms; Local neoplasm recurrence; Molecular typing; Prognosis; Radiotherapy