title: Validation of statistical predictive models meant to select melanoma patients for sentinel lymph node biopsy.
abstract: BACKGROUND
  To identify melanoma patients at sufficiently low risk of nodal metastases who could avoid sentinel lymph node biopsy (SLNB), several statistical models have been proposed based upon patient/tumor characteristics, including logistic regression, classification trees, random forests, and support vector machines. We sought to validate recently published models meant to predict sentinel node status.
  
  
  METHODS
  We queried our comprehensive, prospectively collected melanoma database for consecutive melanoma patients undergoing SLNB. Prediction values were estimated based upon four published models, calculating the same reported metrics: negative predictive value (NPV), rate of negative predictions (RNP), and false-negative rate (FNR).
  
  
  RESULTS
  Logistic regression performed comparably with our data when considering NPV (89.4 versus 93.6%); however, the model's specificity was not high enough to significantly reduce the rate of biopsies (SLN reduction rate of 2.9%). When applied to our data, the classification tree produced NPV and reduction in biopsy rates that were lower (87.7 versus 94.1 and 29.8 versus 14.3, respectively). Two published models could not be applied to our data due to model complexity and the use of proprietary software.
  
  
  CONCLUSIONS
  Published models meant to reduce the SLNB rate among patients with melanoma either underperformed when applied to our larger dataset, or could not be validated. Differences in selection criteria and histopathologic interpretation likely resulted in underperformance. Statistical predictive models must be developed in a clinically applicable manner to allow for both validation and ultimately clinical utility.
authors.affiliation: Department of Surgery, University of Michigan Health System, 3304 Cancer Center, 1500 East Medical Center Drive, Ann Arbor, MI, 48109-0932, USA. msabel@umich.edu
authors.forename: Michael S
authors.initials: MS
authors.lastname: Sabel
authors.forename: John D
authors.initials: JD
authors.lastname: Rice
authors.forename: Kent A
authors.initials: KA
authors.lastname: Griffith
authors.forename: Lori
authors.initials: L
authors.lastname: Lowe
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Wong
authors.forename: Alfred E
authors.initials: AE
authors.lastname: Chang
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Johnson
authors.forename: Jeremy M G
authors.initials: JM
authors.lastname: Taylor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology / Q000601:surgery*; D008297:Male; D008545:Melanoma / Q000145:classification / Q000473:pathology* / Q000601:surgery*; D008875:Middle Aged; D015233:Models, Statistical; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D021701:Sentinel Lymph Node Biopsy; D060388:Support Vector Machine; D055815:Young Adult