title: Body mass index does not improve the ability to predict biochemical recurrence after radical prostatectomy.
abstract: OBJECTIVE
  To test whether body mass index (BMI) improves pre- or post-operative biochemical recurrence (BCR) predictions after radical prostatectomy.
  
  
  METHODS
  Pre- and post-operative data were available in 2416 and 2499 men, respectively. Cox regression models addressed the association between BMI and the rate of BCR after adjusting for pre- and post-operative predictors. Predictive accuracy was quantified using Harrell's concordance index, with and without BMI and subjected to 200 bootstraps to reduce overfit bias. Differences in predictive accuracy were compared using the Mantel-Haenszel test.
  
  
  RESULTS
  After adjusting for either pre- or post-operative variables, increasing BMI was a statistically independent risk factor of BCR in both models (both p0.003). Its addition to pre- and post-operative variables respectively increased predictive accuracy measures from 69.6 to 70.2% (+0.6%, p=0.7) and from 78.1 to 78.4% (+0.3%, p=0.8).
  
  
  CONCLUSIONS
  Our data emphasise that despite its significance, inclusion of BMI into models, to predict BCR, does not improve their accuracy.
authors.affiliation: Cancer Prognostics and Health Outcomes Unit, University of Montreal Health Centre (CHUM), 1058, rue St-Denis, Montreal, Quebec H2X 3J4, Canada.
authors.forename: Felix K H
authors.initials: FK
authors.lastname: Chun
authors.forename: Alberto
authors.initials: A
authors.lastname: Briganti
authors.forename: Markus
authors.initials: M
authors.lastname: Graefen
authors.forename: Andreas
authors.initials: A
authors.lastname: Erbersdobler
authors.forename: Jochen
authors.initials: J
authors.lastname: Walz
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schlomm
authors.forename: Mirja
authors.initials: M
authors.lastname: Meschke
authors.forename: Alexander
authors.initials: A
authors.lastname: Haese
authors.forename: Luc
authors.initials: L
authors.lastname: Valiquette
authors.forename: Hartwig
authors.initials: H
authors.lastname: Huland
authors.forename: Pierre I
authors.initials: PI
authors.lastname: Karakiewicz
mesh_terms: D015992:Body Mass Index; D018572:Disease-Free Survival; D006801:Humans; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis*; D011184:Postoperative Period; D011379:Prognosis; D011468:Prostatectomy / Q000706:statistics & numerical data*; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000601:surgery*; D012044:Regression Analysis; D012680:Sensitivity and Specificity