title: Difference between observed and expected number of involved lymph nodes reflects the metastatic potential of breast cancer independent to intrinsic subtype.
abstract: OBJECTIVE
  Poor prognosis associated with metastasis in breast cancer patients highlights the critical need to develop an effective evaluation model for metastatic potential (MP). We hypothesized that MP could be also indicated by primary tumor size and involved lymph nodes (LNs).
  
  
  METHODS
  The expected number of involved LNs is defined as tumor size (cm) divided by 1.5. The effect of the surrogate for MP (defined as difference between the number of observed and expected involved LNs) on breast cancer-specific survival (BCSS) was investigated in the first cohort from SEER (n = 108,814). Validation was performed in another SEER cohort (n = 50,414) and a third cohort (n = 3,755).
  
  
  RESULTS
  MP is an independent predictor for BCSS in the overall population [hazard ratio (HR) for high MP: 2.92; 95% confidence interval (CI): 2.80-3.03] and in subgroups. The effect of surrogate for MP on survival was independent to intrinsic subtype, with adjusted HRs of 3.46 (95%CI, 2.02-5.93), 2.30 (95%CI, 1.64-3.24), 4.05 (95%CI, 2.85-5.76), and 1.45 (95%CI, 1.04-2.03) in luminal-A, luminal-B, triple-negative, and HER2-positive subtypes, respectively.
  
  
  CONCLUSIONS
  Difference between the observed and expected number of involved LNs serves as an indicator for MP, which is independent to intrinsic subtype and could predict survival. Our findings need further validation.
authors.affiliation: Department of Breast Surgery, Cancer Center and Cancer Institute, Shanghai Medical College, Fudan University, Shanghai, P.R. China.
authors.forename: Ke-Da
authors.initials: KD
authors.lastname: Yu
authors.affiliation: Department of Breast Surgery, Cancer Center and Cancer Institute, Shanghai Medical College, Fudan University, Shanghai, P.R. China.
authors.forename: Yi-Zhou
authors.initials: YZ
authors.lastname: Jiang
authors.affiliation: Department of Breast Surgery, Cancer Center and Cancer Institute, Shanghai Medical College, Fudan University, Shanghai, P.R. China.
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Shao
mesh_terms: D014408:Biomarkers, Tumor; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000145:classification / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000473:pathology*; D008875:Middle Aged; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D018426:SEER Program
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: breast cancer; lymph node; metastatic potential