title: Contemporary external validation of the Leibovich model for prediction of progression after radical surgery for clear cell renal cell carcinoma.
abstract: OBJECTIVE
  The aim of this study was to externally validate in an up-to-date setting the predictive ability of the model for recurrence after radical treatment of clear cell renal cell carcinoma (CCRCC) published by Leibovich in 2003.
  
  
  METHODS
  The study included a total of 386 consecutive patients with CCRCC between January 1997 and May 2013, treated with partial or radical nephrectomy. All patients were scored with points between 0 and 11, and further subdivided into low-, intermediate- and high-risk groups according to the original paper. Well-recognized statistical methods for the evaluation of Cox's proportional hazard-based prognostic models were applied. To validate the discriminative ability, Harrell's concordance (c) index and hazard ratios (HRs) between risk groups were used, and calibration was graphically explored.
  
  
  RESULTS
  The 10 year recurrence-free survival rates for the low-, intermediate- and high-risk groups were 87.3%, 63.8% and 19.8%, respectively Harrell's c index was 0.864. The HRs across risk groups for the intermediate- and high-risk groups were 5.29 and 21.56, respectively, with the low-risk group as a reference category. A gross comparison of the survival estimates between the patients showed an overall similarity. However, differences within the intermediate- and high-risk groups were seen in the first year of follow-up.
  
  
  CONCLUSIONS
  The Leibovich model seems to discriminate well between risk groups, but for the intermediate- and high-risk groups the calibration is not optimal. This study validates the model in a present-day Nordic patient population. The model can be used as a risk stratification tool for follow-up after radical treatment of CCRCC.
authors.affiliation: Departments of Urology.
authors.forename: Christian
authors.initials: C
authors.lastname: Beisland
authors.forename: Gigja
authors.initials: G
authors.lastname: Gudbrandsdottir
authors.forename: Lars A R
authors.initials: LA
authors.lastname: Reisæter
authors.forename: Leif
authors.initials: L
authors.lastname: Bostad
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Karin M
authors.initials: KM
authors.lastname: Hjelle
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D018450:Disease Progression; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology; D009392:Nephrectomy / Q000379:methods*; D009664:Norway / Q000453:epidemiology; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors; D015996:Survival Rate; D016896:Treatment Outcome
keywords: Clear cell renal cell carcinoma; external validation; follow-up; integrated staging systems; prognostic risk groups; recurrence