title: Lack of either estrogen or progesterone receptor expression is associated with poor survival outcome among luminal A breast cancer subtype.
abstract: BACKGROUND
  This study was designed to evaluate the impact of lack of either estrogen receptor (ER) or progesterone receptor (PR) on characteristics and outcomes among luminal A breast cancer subtype treated with endocrine with or without chemotherapeutic agents.
  
  
  METHODS
  The luminal A subtype was categorized into three subgroups: ER+/PR+, ER+/PR-, and ER-/PR+. All tumors were human epidermal growth factor receptor 2 (HER2) negative. Clinicopathological features and survival were analyzed using the Severance Hospital dataset (n = 1,180) and were validated by the nationwide Korean Breast Cancer Society (KBCS) registry (n = 9,916).
  
  
  RESULTS
  Despite the different distribution of ER/PR status, tumor stage, grade, and local therapies between the two datasets, similarly ER+/PR+ showed smaller size and good differentiation, ER+/PR- patients had the oldest age at diagnosis, and ER-/PR+ was associated with the youngest age at onset and grade III tumor. Single hormone receptor-positive subgroups demonstrated worse disease-related outcomes than the ER+/PR+ subgroup. These associations were confirmed by the KBCS dataset. This trend was also demonstrated in the subpopulation of 1,944 patients with Ki-67 < 14 %. Inferior survival of single receptor-positive tumors was more definite among node-positive patients even when receiving both chemo-endocrine therapies.
  
  
  CONCLUSIONS
  Current results suggest that the luminal A subtype is also heterogeneous and each subgroup has unique clinicopathologic characteristics. Lack of either ER or PR expression is associated with worse survival, especially among node-positive luminal A subtype.
authors.affiliation: Department of Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Seho
authors.initials: S
authors.lastname: Park
authors.forename: Byeong-Woo
authors.initials: BW
authors.lastname: Park
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Chang Wan
authors.initials: CW
authors.lastname: Jeon
authors.forename: Han-Sung
authors.initials: HS
authors.lastname: Kang
authors.forename: Jung-Eun
authors.initials: JE
authors.lastname: Choi
authors.forename: Ki-Tae
authors.initials: KT
authors.lastname: Hwang
authors.forename: In Cheol
authors.initials: IC
authors.lastname: Kim
mesh_terms: D000328:Adult; D000367:Age Factors; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology* / Q000628:therapy; D017024:Chemotherapy, Adjuvant; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D019394:Ki-67 Antigen / Q000378:metabolism; D008875:Middle Aged; D060787:Neoplasm Grading; D009362:Neoplasm Metastasis; D016016:Proportional Hazards Models; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D012042:Registries; D056910:Republic of Korea
chemical_list: D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human