Prospective validation of a risk calculator which calculates the probability of a positive prostate biopsy in a contemporary clinical cohort

Heidi A. van Vugt*, Ries Kranse, Ewout W. Steyerberg, Henk G. van der Poel, Martijn Busstra, Paul Kil, Eric H. Oomens, Igle J. de Jong, Chris H. Bangma, Monique J. Roobol

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

29 Citations (Scopus)

Abstract

Background: Prediction models need validation to assess their value outside the development setting.

Objective: To assess the external validity of the European Randomised study of Screening for Prostate Cancer (ERSPC) Risk Calculator (RC) in a contemporary clinical cohort.

Methods: The RC calculates the probability of a positive sextant prostate biopsy (P(posb)) using serum prostate-specific antigen (PSA), results of digital rectal examination, transrectal ultrasound (TRUS) and ultrasound assessed prostate volume. We prospectively validated the RC in 320 biopsied men (55-75 years), with no previous prostate biopsy, included in five Dutch hospitals in 2008-2011. If the P(posb) was >= 20% a biopsy was recommended. The performance of the RC was tested by comparing the observed outcomes to predicted probabilities, using the area under the curve (AUC) and decision curves analyses.

Results: Compared to the screening cohort, men in the clinical cohort differed. They had higher PSA levels (median 6.8 versus 4.3 ng/ml, p <0.01), less TRUS-lesions (27% versus 34%, p = 0.01) and more prostate cancer (PCa) at biopsy (43% versus 25%, p <0.01). Mainly eight biopsy cores were taken. Despite the differences between these cohorts, the mean observed probability agreed with the mean predicted probability (43% versus 40%). The RC predicted P(posb) better than a model with PSA and digital rectal examination, AUC 0.77 (95% confidence interval (CI) 0.72-0.83) and 0.71 (95% CI 0.65-0.76, p <0.01), respectively. This was confirmed by the decision curves analysis. Under the 20% threshold, 17% (11/63) of the biopsied men were diagnosed with PCa. Two of 11 men had an important cancer (Gleason 3 + 4).

Conclusions: The ERSPC RC performs well in a Dutch clinical cohort in men with previous PSA tests and contemporary biopsy schemes, and outperforms a PSA and DRE-based approach in the decision to perform a biopsy. (C) 2012 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)1809-1815
Number of pages7
JournalEuropean Journal of Cancer
Volume48
Issue number12
DOIs
Publication statusPublished - Aug-2012

Keywords

  • Clinical setting
  • Prediction model
  • Prostate biopsy
  • Prostate cancer
  • Prostate cancer risk calculator
  • Validation
  • CANCER PREVENTION TRIAL
  • PREDICTION
  • ROTTERDAM
  • VOLUME
  • NETHERLANDS
  • DIAGNOSIS
  • BENEFITS
  • PROTOCOL
  • SEXTANT
  • CORE

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