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The 4Kscore Test as a Predictor of High-Grade Prostate Cancer prior to Biopsy
Stephen M. Zappala, MD1, Daniel Lin, MD2, Kimberly Rieger-Christ, PhD3.
1Andover Urology, Andover, MA, USA, 2University of Washington, Seattle, WA, USA, 3Lahey Clinic, Burlington, MA, USA.

INTRODUCTION AND OBJECTIVES: Prostate Specific Antigen (PSA) has modest specificity and most men with elevated PSA do not have prostate cancer (PCa). Hundreds of thousands of negative prostate biopsy (Bx) procedures are conducted each year in the United States (US), and about half of the ~250,000 positive Bx are Gleason Score (GS) = 6. A four kallikrein assay panel of total, free and intact PSA, and human Kallikrein 2 (hK2) combined in an algorithm with age, digital rectal exam (DRE) and prior biopsy status (4Kscore™ test) has been adapted from previous European studies, where the test was found to be an accurate predictor of the result of Bx, and in particular, high-grade disease of GS ≥7. The goal is to replicate the European performance in an independent, prospective, blinded study in the US.
METHODS: The first 300 patients enrolled from Oct. 2013 to Jan. 2014 form this prespecified interim analysis. Enrollment was open to all men scheduled for Bx at 26 US Urology centers. After phlebotomy, a transrectal ultrasound Bx (≥ 10 cores) was performed. The four assays were performed at OPKO Lab, Nashville, TN, a CLIA-certified laboratory. Histopathology was conducted by the established practice at each site. Independent biostatisticians evaluated the laboratory and Bx data.
RESULTS: The 4Kscore test provided a very high degree of discrimination compared to a clinical algorithm built on PSA and clinical data (Table). Calibration of the 4Kscore algorithm was near perfect compared to its European version. For one illustrative cut point, the 4Kscore test would have reduced the number of Bx’s by 41%, with a Negative Predictive Value (NPV) of 97%. Decision analysis demonstrated that clinical decision-making would be improved by the use of the 4Kscore test.
CONCLUSIONS: The 4Kscore test, using fresh samples evaluated in a commercial laboratory, yields superior performance compared with a clinical model. The 4Kscore test reports a probability of finding high-grade cancer that can enhance the clinically relevant, shared decision-making between urologist and patient. The 4Kscore test will have an integral role in the diagnosis and management of prostate cancer. The prospective study is completing its validation phase with an additional 1000 patients in the cohort.
Source of Funding:
Funding for the study was provided by OPKO Diagnostics.


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