title: The number of positive nodes and the ratio of positive to excised nodes are significant predictors of survival in women with micrometastatic node-positive breast cancer.
abstract: BACKGROUND
  To evaluate the prognostic impact of the number of positive nodes and the lymph node ratio (LNR) of positive to excised nodes on survival in women diagnosed with nodal micrometastatic breast cancer before the era of widespread sentinel lymph node biopsy.
  
  
  METHODS
  Subjects were 62,551 women identified by the Surveillance Epidemiology and End Results database, diagnosed with pT1-2pN0-1 breast cancer between 1988 and 1997. Kaplan-Meier breast cancer-specific survival (BCSS) and overall survival (OS) were compared between three cohorts: node-negative (pN0, n=57,980) nodal micrometastasis all <or=2mm (pNmic, N=1818), and macroscopic nodal metastasis >2mm but <2 cm (pNmac, n=2753). Nodal subgroups were examined by the number of positive nodes (1-3 versus >or= 4) and the LNR (<or=0.25 versus >0.25).
  
  
  RESULTS
  Median follow-up was 7.3 yr. Ten-year BCSS and OS in pNmic breast cancer were significantly lower compared to pN0 disease (BCSS 82.3% versus 91.9%, p<0.001 and OS 68.1% versus 75.7%, p<0.001). BCSS and OS with pNmic disease progressively declined with increasing number of positive nodes and increasing LNR. OS with pNmic was similar to pNmac disease when matched by the number of positive nodes and by the LNR. Both pN-based and LNR-based classifications were significantly prognostic of BCSS and OS on Cox regression multivariate analysis.
  
  
  CONCLUSIONS
  Nodal micrometastasis is associated with poorer survival compared to pN0 disease. Mortality hazards with nodal micrometastasis increased with increasing number of positive nodes and increasing LNR. The number of positive nodes and the LNR should be considered in risk estimates for patients with nodal micrometastatic breast cancer.
authors.affiliation: Department of Radiation Oncology, British Columbia Cancer Agency, Vancouver Island Centre, University of British Columbia, Victoria, BC, Canada. ptruong@bccancer.bc.ca
authors.forename: Pauline T
authors.initials: PT
authors.lastname: Truong
authors.forename: Vincent
authors.initials: V
authors.lastname: Vinh-Hung
authors.forename: Gabor
authors.initials: G
authors.lastname: Cserni
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Woodward
authors.forename: Patricia
authors.initials: P
authors.lastname: Tai
authors.forename: Georges
authors.initials: G
authors.lastname: Vlastos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011379:Prognosis; D018570:Risk Assessment; D016019:Survival Analysis; D016896:Treatment Outcome