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

OBJECTIVES: The use of mpMRI has been a significant advance in the diagnosis of clinically significant prostate cancer (ISUP Grade Group ≥2, csPCa) and is recommended in most current guidelines. Proclarix® is a novel CE-marked biomarker test aiding in the identification of csPCa. The aim of the study was the assessment of the clinical performance of Proclarix alone or in combination with mpMRI to predict csPCa.

PATIENTS AND METHODS: The study included blood samples from 721 men undergoing mpMRI followed by biopsy at University College London (UCL), 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% NPV and 66% PPV. The Proclarix-MRI score's specificity (68%) was significantly (p<0.001) better compared to MRI-ERSPC risk score (51%), Proclarix (27%) or mpMRI (28%) alone. In addition, Proclarix by itself was found to be useful in the MRI PI-RADS 3 subgroup by outperforming PSA 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 3 mpMRI. Despite these encouraging results, further validation is needed.