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    Liquid biopsy tests for prostate Ca show low congruence

    Two commercially available blood specimen tests have shown low congruence for tumor-specific alterations, according to authors of a recently published analysis including 40 paired samples from patients with metastatic prostate cancer.

    Despite the limited sample size, the data suggest that gene alterations reported by so-called “liquid biopsy” tests will be different across platforms, “raising the specter that patients could potentially receive different treatments depending on the cell-free DNA (cfDNA) platform,” the authors wrote in a research letter published online in JAMA Oncology (Dec. 14, 2017).

    Individually, the two liquid biopsy tests both have “self-reported high accuracy, specificity, and sensitivity to specifically detect and quantify tumor-specific alterations,” wrote co-authors Gonzalo Torga, MD, and Kenneth J. Pienta, MD, of the James Buchanan Brady Urological Institute at Johns Hopkins School of Medicine, Baltimore.

    The initial intention of the study was to find the best commercial lab to test samples for metastatic prostate cancer patients, Dr. Torga said in an interview with Urology Times.

    However, “when we compared the results, we were stricken by the discordance, and we believed it was very important to share our data with the medical community,” Dr. Torga said of the study, which is believed to be the first to compare two liquid biopsy providers in the clinical setting.

    Of 34 evaluable patient specimens, only nine (35%) showed complete congruence between the two assays, which included Guardant360 (Guardant Health, Inc.) and PlasmaSELECT (Personal Genome Diagnostics Inc.), the authors said in their report.

    Among the remaining 25 specimens, investigators said they found partial congruence in six, and no congruence in 16.

    Next: Findings 'disturbing,' says editorial author

    Andrew Bowser
    Andrew Bowser is a medical writer based in Brooklyn, New York.


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