Purpose: We sought to externally validate recently published prostate cancer risk calculators incorporating multiparametric magnetic resonance imaging to predict clinically significant prostate cancer. We also compared the performance of these calculators to that of multiparametric magnetic resonance imaging naïve prostate cancer risk calculators.
Materials and methods: We identified men without a previous prostate cancer diagnosis who underwent transperineal template saturation prostate biopsy with fusion guided targeted biopsy between November 2014 and March 2018 at our academic tertiary referral center. Any Gleason pattern 4 or greater was defined as clinically significant prostate cancer. Predictors, which were patient age, prostate specific antigen, digital rectal examination, prostate volume, family history, previous prostate biopsy and the highest region of interest according to the PI-RADS™ (Prostate Imaging Reporting and Data System), were retrospectively collected. Four multiparametric magnetic resonance imaging prostate cancer risk calculators and 2 multiparametric magnetic resonance imaging naïve prostate cancer risk calculators were evaluated for discrimination, calibration and the clinical net benefit using ROC analysis, calibration plots and decision curve analysis.
Results: Of the 468 men 193 (41%) were diagnosed with clinically significant prostate cancer. Three multiparametric magnetic resonance imaging prostate cancer risk calculators showed similar discrimination with a ROC AUC significantly higher than that of the other prostate cancer risk calculators (AUC 0.83-0.85 vs 0.69-0.74). Calibration in the large showed 2% deviation from the true amount of clinically significant prostate cancer for 2 multiparametric magnetic resonance imaging risk calculators while the other calculators showed worse calibration at 11% to 27%. A clinical net benefit was observed only for 3 multiparametric magnetic resonance imaging risk calculators at biopsy thresholds of 15% or greater. None of the 6 investigated prostate cancer risk calculators demonstrated clinical usefulness against a biopsy all strategy at thresholds less than 15%.
Conclusions: The performance of multiparametric magnetic resonance imaging prostate cancer risk calculators varies but they generally outperform multiparametric magnetic resonance imaging naïve prostate cancer risk calculators in regard to discrimination, calibration and clinical usefulness. External validation in other biopsy settings is highly encouraged.
Keywords: biopsy; clinical decision rules; magnetic resonance imaging; prostatic neoplasms; risk.