title: Robust and validated models to predict high risk of non-sentinel node metastases in breast cancer patients with micrometastases or isolated tumor cells in the sentinel node.
abstract: BACKGROUND
  Benefit from axillary lymph node dissection in sentinel node positive breast cancer patients is under debate. Based on data from 1820 Danish breast cancer patients operated in 2002-2008, we have developed two models to predict high risk of non-sentinel node metastases when micrometastases or isolated tumor cells are found in sentinel node. The aim of this study was to validate these models in an independent Danish dataset.
  
  
  METHODS
  We included 720 breast cancer patients with micrometastases and 180 with isolated tumor cells in sentinel node operated in 2009-2010 from the Danish Breast Cancer Cooperative Group database. Accuracy of the models was tested in this cohort by calculating area under the receiver operating characteristic curve (AUC) as well as sensitivity and specificity.
  
  
  RESULTS
  AUC for the model for patients with micrometastases was comparable to AUC in the original cohort: 0.63 and 0.64, respectively. The sensitivity and specificity for predicting risk of non-sentinel node metastases over 30% was 0.36 and 0.81, respectively, in the validation cohort. AUC for the model for patients with isolated tumor cells decreased from 0.73 in the original cohort to 0.60 in the validation cohort. When dividing patients with isolated tumor cells into high and low risk of non-sentinel node metastases according to number of risk factors present, 37% in the high-risk group had non-sentinel node metastases. Specificity and sensitivity was 0.48 and 0.88, respectively, in the validation cohort when using this cut-point.
  
  
  CONCLUSIONS
  In this independent dataset, the model for patients with micrometastases was robust with accuracy similar to the original cohort, while the model for patients with isolated tumor cells was less accurate. The models may be used to identify patients where axillary lymph node dissection should still be considered.
authors.affiliation: Department of Breast Surgery, Copenhagen University Hospital , Copenhagen , Denmark.
authors.forename: Tove F
authors.initials: TF
authors.lastname: Tvedskov
authors.forename: Maj-Britt
authors.initials: MB
authors.lastname: Jensen
authors.forename: Eva
authors.initials: E
authors.lastname: Balslev
authors.forename: Niels
authors.initials: N
authors.lastname: Kroman
mesh_terms: D019540:Area Under Curve; D001943:Breast Neoplasms / Q000473:pathology*; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000473:pathology*; D008954:Models, Biological; D061206:Neoplasm Micrometastasis; D012372:ROC Curve; D012307:Risk Factors; D021701:Sentinel Lymph Node Biopsy