Urine test accurately predicts high-grade prostate Ca

June 5, 2015

An experimental assay could reduce the need for prostate needle biopsies, researchers say.

A new urine test shows high sensitivity and negative predictive value (NPV) for diagnosing high-grade prostate cancer and could reduce the need for prostate needle biopsies, researchers reported at the AUA annual meeting in New Orleans. 

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A multicenter study led by researchers from New York-Presbyterian/Columbia University Medical Center, New York found a sensitivity of 92% and an NPV of 91% for the liquid biopsy test, EXO106. The test produced markedly better diagnostic results for high-grade prostate cancer (Gleason score >7) than standard of care-PSA in combination with age, race, and family history of prostate cancer.

EXO106 is an exosomal gene expression assay that evaluates messenger RNA in exosomes excreted in urine to detect cancer genes. The assay looks for three specific genes indicative of high-grade prostate cancer on exosomal RNA: ERG, PCA3, and SPDEF.

The authors prospectively enrolled 1,560 men from 25 urology practices nationwide who were 50 years of age or older, had equivocal PSA levels of 2.0 ng/mL to 10.0 ng/mL, had never had a prostate biopsy, and were scheduled for an initial biopsy for possible prostate cancer. They collected first-catch urine specimens not associated with digital rectal examination (DRE). Nine percent of the urine samples were excluded, leaving a training set of 499 patients and an intended-use population of 519 patients (median age 63 years, media PSA 5.12 ng/mL, 18% suspicious DRE, 28% family history of prostate cancer).

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Analysis of the EXO106 assay results demonstrated diagnostic performance clearly superior to standard of care with an area under the curve (AUC) of 0.711 for EXO106 alone compared with 0.631 for standard of care and 0.545 for PSA alone, reported the researchers, led by James McKiernan, MD, of New York-Presbyterian/Columbia University Medical Center, who presented the study results. The AUC for EXO106 plus standard of care was 0.725.

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EXO106 showed a sensitivity of 91.89%, specificity of 33.96%, NPV of 91.30%, and positive predictive value of 35.70%. The test had a false-positive rate of less than 5% for cancers with a Gleason score of 4+3 or higher and found more than 90% of high-grade cancers that were confirmed by biopsy.

EXO106 has the potential to reduce needle biopsies by 27% among men with indeterminate PSA scores, the authors conclude.

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The study validates interim results from a prospective, observational, multi-institutional trial of 255 patients, in which EXO106 showed an NPV of 96% and an AUC of 0.74 for differentiating higher-risk cancers, the authors note. The test, still in trial stages, hasn’t been approved by the FDA.

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EXO106 is the first assay of its kind for prostate cancer, and shows promise both for detecting cancer and differentiating among its various grades, says Dr. McKiernan.

“We are extremely encouraged by these results and the potential significance this liquid biopsy test may have for men with prostate cancer,” said co-author Gerald L. Andriole, Jr., MD, of Washington University School of Medicine in St. Louis. “These data demonstrate the clinical utility of exosomes to reveal critical molecular information about the aggressiveness of prostate cancer. They also signal the potential to leverage the benefits of precision medicine prior to initial biopsy, possibly forging a completely new paradigm for prostate cancer screening and treatment.”

Several study co-authors are consultant/advisers for or employees of Exosome Diagnostics.

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