title: Validation of a bone scan positivity risk table in non-metastatic castration-resistant prostate cancer.
abstract: OBJECTIVE
  To test the external validity of a previously developed risk table, designed to predict the probability of a positive bone scan among men with non-metastatic (M0) castration-resistant prostate cancer (CRPC), in a separate cohort.
  
  
  METHODS
  We retrospectively analysed 429 bone scans of 281 patients with CRPC, with no known previous metastases, treated at three Veterans Affairs Medical Centers. We assessed the predictors of a positive scan using generalized estimating equations. Area under the curve (AUC), calibration plots and decision-curve analysis were used to assess the performance of our previous model to predict a positive scan in the current data.
  
  
  RESULTS
  A total of 113 scans (26%) were positive. On multivariable analysis, the only significant predictors of a positive scan were log-transformed prostate-specific antigen (PSA): hazard ratio (HR) 2.13; 95% confidence interval (CI) 1.71-2.66 (P < 0.001) and log-transformed PSA doubling time (PSADT): HR 0.53; 95% CI 0.41-0.68 (P < 0.001). Among men with a PSA level <5 ng/mL, the rate of positive scans was 5%. The previously developed risk table had an AUC of 0.735 to predict positive bone scan with excellent calibration, and provided additional net benefit in the decision-curve analysis.
  
  
  CONCLUSIONS
  We have validated our previously developed table to predict the risk of a positive bone scan among men with M0/Mx CRPC. Use of this risk table may allow better tailoring of patients' scanning to identify metastases early, while minimizing over-imaging. Regardless of PSADT, positive bone scans were rare in men with a PSA <5 ng/mL.
authors.affiliation: Division of Urology, Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, CA, USA. stephen.freedland@cshs.org.|Urology Section, Veterans Affairs Medical Center, Durham, NC, USA. stephen.freedland@cshs.org.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Freedland
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.|Department of Biostatistics and Bioinformatics, Duke University School of Medicine, Durham, NC, USA.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Howard
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Hanyok
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.
authors.forename: Vishnu K
authors.initials: VK
authors.lastname: Kadiyala
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.
authors.forename: Jameson Y
authors.initials: JY
authors.lastname: Kuang
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.
authors.forename: Colette A
authors.initials: CA
authors.lastname: Whitney
authors.affiliation: Urology Section, Veterans Affairs Medical Center, Durham, NC, USA.
authors.forename: Floyd R
authors.initials: FR
authors.lastname: Wilks
authors.affiliation: Department of Urology, University of California at San Diego Medical Center, San Diego, CA, USA.|Urology Section, Veterans Affairs Medical Center, San Diego, CA, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kane
authors.affiliation: Urology Section, Division of Surgery, Veterans Affairs Medical Centers, Augusta, GA, USA.|Division of Urologic Surgery, Department of Surgery, Medical College of Georgia, Augusta, GA, USA.
authors.forename: Martha K
authors.initials: MK
authors.lastname: Terris
authors.affiliation: Division of Urology, Department of Surgery, Oregon Health and Science University, Portland, OR, USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Amling
authors.affiliation: Departments of Urology and Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.|Urology Section, Department of Surgery, Veterans Affairs Medical Center, San Francisco, CA, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Cooperberg
authors.affiliation: Urology Section, Department of Surgery, Veterans Affairs Medical Center, Los Angeles, CA, USA.|Department of Urology, University of California at Los Angeles Medical Center, Los Angeles, CA, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Aronson
authors.affiliation: Department of Urology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Moreira
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000556:secondary*; D006801:Humans; D008297:Male; D064129:Prostatic Neoplasms, Castration-Resistant / Q000473:pathology*; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D018570:Risk Assessment
keywords: metastasis; prostate cancer; prostate-specific antigen; validation studies