Accurate diagnosis of prostate cancer by combining Proclarix with magnetic resonance imaging

Objectives To assess of the clinical performance of Proclarix ® (a novel Conformité Européenne [CE]‐marked biomarker test aiding in the identification of clinically significant prostate cancer [csPCa]) alone or in combination with multiparametric magnetic resonance imaging (mpMRI) to predict csPCa (International Society of Urological Pathology Grade Group ≥2). Patients and Methods The study included blood samples from 721 men undergoing mpMRI followed by biopsy at University College London, London, and Vall d’Hebron University Hospital, Barcelona. Samples were tested blindly. The Proclarix‐MRI model combining prostate volume, Proclarix and mpMRI results was trained using the UCL cohort ( n = 159) and validated in the Vall d’Hebron cohort ( n = 562). Its diagnostic performance was established in correlation to biopsy outcome and compared to available clinical parameters and risk calculators. Results Clinical performance of the Proclarix‐MRI model in the validation cohort did not significantly differ from the training cohort and resulted in a sensitivity for csPCa of 90%, 90% negative predictive value and 66% positive predictive value. The Proclarix‐MRI score's specificity (68%) was significantly ( P < 0.001) better than the MRI‐European Randomized study of Screening for Prostate Cancer risk score (51%), Proclarix (27%) or mpMRI (28%) alone. In addition, Proclarix by itself was found to be useful in the MRI Prostate Imaging‐Reporting and Data System (PI‐RADS) score 3 subgroup by outperforming prostate‐specific antigen density in terms of specificity (25% vs 13%, P = 0.004) at 100% sensitivity. Conclusion When combined with mpMRI and prostate volume, Proclarix reliably predicted csPCa and ruled out men with no or indolent cancer. A large reduction of two thirds of unneeded biopsies was achieved. Proclarix can further be used with high confidence to reliably detect csPCa in men with an indeterminate PI‐RADS score 3 mpMRI. Despite these encouraging results, further validation is needed.