Clinical Validation of IsoPSA, a Single Parameter, Structure-Based Assay for Improved Detection of High-Grade Prostate Cancer.

Current PSA markers for prostate cancer detection are limited by low specificity for high-grade disease. IsoPSA is a blood-based, structure-focused assay that predicts risk by partitioning isoforms of PSA that are linked to cancer in an aqueous two-phase reagent system. We validated the clinical performance of IsoPSA in identifying the presence of high-grade disease in a new contemporary biopsy cohort.

Multicenter prospective validation of 271 men scheduled for prostate biopsy at seven academic and community centers enrolled between May-2017 and March-2018. Blood samples were obtained for IsoPSA prior to biopsy. Discrimination power of IsoPSA for the detection of high-grade prostate cancer (Gleason>7) was evaluated using ROC analysis and compared to prior results. Clinical performance was further improved upon comparison against multiparametric magnetic resonance imaging-ultrasound (mpMRI-US) vs. transrectal-ultrasound (TRUS) guided biopsies.

The AUC for IsoPSA was 0.784 for high-grade vs. low-grade cancer/benign histology - superior to both total PSA and % free PSA. For 1000 patients being biopsied, use of IsoPSA would have reduced unnecessary biopsies by 43% (from 705 to 402), with only 22 missed high-grade cancers, of which only 7 would have been Gleason sum 4+3 or higher. Subset analysis of mpMRI-guided biopsy produced a substantial improvement of the AUC to 0.831.

Validation of the structure-based IsoPSA assay demonstrated statistical concordance with previously reported results and verified its superior performance vs. concentration-based PSA and %fPSA. IsoPSA improvement in detecting high-grade PCa using mpMRI-US guided biopsy may help to define a new diagnostic paradigm.

The Journal of urology. 2019 Feb 15 [Epub ahead of print]

Mark Stovsky, Eric A Klein, Arnon Chait, Kannan Manickam, Andrew J Stephenson, Mathew Wagner, Martin Dineen, Yair Lotan, Alan Partin, Jack Baniel, Aimee Kestranek, Prasad Gawande, Boris Zaslavsky

Department of Urology, Glickman Urological and Kidney Institute, Cleveland Clinic , Cleveland , Ohio ., Cleveland Diagnostics, Inc. , Cleveland , Ohio ., Chesapeake Urology Associates , Baltimore , MD ., Kaiser Permanente Northwest , Clackamas , OR ., Advanced Urology Institute , Daytona Beach , FL., The University of Texas Southwestern Medical Center , Dallas , TX ., The Brody Urological Institute at The Johns Hopkins University , Baltimore , MD ., Rabin Medical Center , Petah-Tikva , Israel.

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