External Validation of MRI-Based Prostate Cancer Risk Calculators in a Contemporary Pre-Biopsy mpMRI Cohort
- 1Department of Urology, Paracelsus Medical University Salzburg, 5020 Salzburg, Austria
Abstract
Background: Multiparametric MRI (mpMRI)-integrated risk calculators may improve individualized prediction of clinically significant prostate cancer (csPCa) before biopsy. We externally validated and directly compared the MRI-based Radtke and Alberts risk calculators (Radtke-RC and Alberts-RC) in a contemporary MRI-selected biopsy cohort, assessing discrimination, calibration, and clinical utility. Methods: Consecutive patients undergoing pre-biopsy mpMRI followed by combined MRI-targeted and systematic biopsy were retrospectively identified. The primary endpoint was csPCa, defined as ISUP Grade Group ≥ 2. Discrimination was assessed using receiver operating characteristic analysis, calibration using observed-to-expected (O:E) ratios, calibration-in-the-large (slope fixed at 1), calibration slopes, and calibration plots, and clinical utility using decision curve analysis. Radtke-RC validation was restricted to biopsy-naïve patients, while head-to-head comparisons were restricted to biopsy-naïve patients evaluable for both calculators. Threshold probabilities of 12%, 20%, and 30% were examined, with bootstrap confidence intervals for incremental net benefit. Results: Of 171 screened patients, seven had no evaluable biopsy outcome. The Radtke-RC validation cohort comprised 144 biopsy-naïve patients, including 55 (38.2%) with csPCa. The Alberts-RC was evaluable in 114 patients; 50 patients could not be assessed because age, prostate volume, or PSA values were outside the online calculator’s permitted input ranges. The common biopsy-naïve cohort comprised 97 patients, including 34 (35.1%) with csPCa. In the model-specific cohorts, AUCs were 0.765 (95% CI 0.682–0.848) for the Radtke-RC and 0.767 (95% CI 0.672–0.861) for the Alberts-RC. In the common cohort, AUCs were 0.774 (95% CI 0.672–0.875) and 0.768 (95% CI 0.661–0.874), respectively, with no statistically significant paired difference (0.006, 95% CI −0.028 to 0.040; p = 0.726). Calibration differed substantially: the Radtke-RC overpredicted risk (mean predicted risk 48.2%; O:E 0.727), whereas the Alberts-RC underpredicted risk (18.0%; O:E 1.944). At thresholds of 12%, 20%, and 30%, the Radtke-RC classified zero, seven, and 25 patients below threshold and missed zero, zero, and four csPCa cases, respectively; corresponding values for the Alberts-RC were 42, 64, and 78 patients below threshold, with seven, 12, and 20 csPCa cases missed. Sensitivity analyses indicated less favourable Radtke-RC decision-analytic performance outside the common cohort, whereas restriction to PI-RADS 4–5 patients did not materially alter relative discrimination. Conclusions: No statistically significant difference in discrimination between the Radtke-RC and Alberts-RC was detected, although the study was not powered to establish equivalence. Despite similar discrimination, the calculators showed substantially different calibration and threshold-specific clinical consequences. In this MRI-selected population, interpretation of fixed risk thresholds should therefore account for calibration, patient selection, and the trade-off between biopsy avoidance and missed csPCa.
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BibTeX
@article{grießner2026external,
title = {{External Validation of MRI-Based Prostate Cancer Risk Calculators in a Contemporary Pre-Biopsy mpMRI Cohort}},
author = {Hubert Grießner and Sarah K. Luck and Julia K. Peters and Kathrin Olesch and Manuel Schlachter and Lukas Oberhammer and Maximilian Pallauf and Lukas Lusuardi and Philipp N. Haid},
journal = {Journal of Clinical Medicine},
year = {2026},
month = oct,
doi = {10.3390/jcm15208146},
url = {https://www.mdpi.com/2077-0383/15/20/8146},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - External Validation of MRI-Based Prostate Cancer Risk Calculators in a Contemporary Pre-Biopsy mpMRI Cohort
AU - Hubert Grießner
AU - Sarah K. Luck
AU - Julia K. Peters
AU - Kathrin Olesch
AU - Manuel Schlachter
AU - Lukas Oberhammer
AU - Maximilian Pallauf
AU - Lukas Lusuardi
AU - Philipp N. Haid
PY - 2026
DA - 2026/10/20
JO - Journal of Clinical Medicine
DO - 10.3390/jcm15208146
UR - https://www.mdpi.com/2077-0383/15/20/8146
AB - Background: Multiparametric MRI (mpMRI)-integrated risk calculators may improve individualized prediction of clinically significant prostate cancer (csPCa) before biopsy. We externally validated and directly compared the MRI-based Radtke and Alberts risk calculators (Radtke-RC and Alberts-RC) in a contemporary MRI-selected biopsy cohort, assessing discrimination, calibration, and clinical utility. Methods: Consecutive patients undergoing pre-biopsy mpMRI followed by combined MRI-targeted and systematic biopsy were retrospectively identified. The primary endpoint was csPCa, defined as ISUP Grade Group ≥ 2. Discrimination was assessed using receiver operating characteristic analysis, calibration using observed-to-expected (O:E) ratios, calibration-in-the-large (slope fixed at 1), calibration slopes, and calibration plots, and clinical utility using decision curve analysis. Radtke-RC validation was restricted to biopsy-naïve patients, while head-to-head comparisons were restricted to biopsy-naïve patients evaluable for both calculators. Threshold probabilities of 12%, 20%, and 30% were examined, with bootstrap confidence intervals for incremental net benefit. Results: Of 171 screened patients, seven had no evaluable biopsy outcome. The Radtke-RC validation cohort comprised 144 biopsy-naïve patients, including 55 (38.2%) with csPCa. The Alberts-RC was evaluable in 114 patients; 50 patients could not be assessed because age, prostate volume, or PSA values were outside the online calculator’s permitted input ranges. The common biopsy-naïve cohort comprised 97 patients, including 34 (35.1%) with csPCa. In the model-specific cohorts, AUCs were 0.765 (95% CI 0.682–0.848) for the Radtke-RC and 0.767 (95% CI 0.672–0.861) for the Alberts-RC. In the common cohort, AUCs were 0.774 (95% CI 0.672–0.875) and 0.768 (95% CI 0.661–0.874), respectively, with no statistically significant paired difference (0.006, 95% CI −0.028 to 0.040; p = 0.726). Calibration differed substantially: the Radtke-RC overpredicted risk (mean predicted risk 48.2%; O:E 0.727), whereas the Alberts-RC underpredicted risk (18.0%; O:E 1.944). At thresholds of 12%, 20%, and 30%, the Radtke-RC classified zero, seven, and 25 patients below threshold and missed zero, zero, and four csPCa cases, respectively; corresponding values for the Alberts-RC were 42, 64, and 78 patients below threshold, with seven, 12, and 20 csPCa cases missed. Sensitivity analyses indicated less favourable Radtke-RC decision-analytic performance outside the common cohort, whereas restriction to PI-RADS 4–5 patients did not materially alter relative discrimination. Conclusions: No statistically significant difference in discrimination between the Radtke-RC and Alberts-RC was detected, although the study was not powered to establish equivalence. Despite similar discrimination, the calculators showed substantially different calibration and threshold-specific clinical consequences. In this MRI-selected population, interpretation of fixed risk thresholds should therefore account for calibration, patient selection, and the trade-off between biopsy avoidance and missed csPCa.
SN - 2077-0383
ER -