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TMRPSS2:ERG superior predictor for prostate cancer biopsy outcome
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TMRPSS2:ERG, a highly specific gene-fusion biomarker, outperformed serum PSA and the Prostate Cancer Prevention Trial risk calculator when predicting prostate cancer biopsy outcome.
In addition, TMPRSS2:ERG distinguished between significant vs. insignificant cancer on biopsy by the Epstein criteria, said John T. Wei, MD, MS, professor of urology at the University of Michigan.
“This new T2:ERG urinary assay has the ability to not only detect prostate cancer but may help move us forward in our paradigm to detect clinically significant prostate cancer,” Wei said. He added that further individual trials will evaluate the value of the assay.
Researchers at three institutions prospectively collected evaluable post-digital rectal exam urine specimens from 635 men referred for biopsy and/or prostatectomy. TMPRSS2:ERG mRNA copies in samples were quantified using a transcription-mediated amplification assay and normalized to PSA mRNA copies then multiplied by 100,000 to get a TMPRSS2:ERG score.
Wei said that for predicting prostate cancer biopsy outcome in both individual and combined biopsy cohorts (n=572), TMRPSS2:ERG had superior area under the curve (0.72) compared with serum PSA (0.60) or the Prostate Cancer Prevention Trial (PCPT) risk calculator (0.64).
Researchers found that among the 101 men in the cohort who underwent prostatectomy, higher TMPRSS2:ERG score was associated with upgrading at prostatectomy (biopsy Gleason score 6 to prostatectomy Gleason score 7) and high prostatectomy Gleason Score (>6 vs. < 6), but not prostate weight (R=–0.20).
Wei said that the T2:ERG assay added to the diagnostic value of the PCPT nomogram. Alone, PCPT risk score area under the curve was 0.65. When T2:ERG is added to PCPT risk score, area under the curve was 0.75.
“On average, the T2:ERG assay appears to increase the area under the curve by 10%,” he said. “Clinically, I would submit to you that’s a significant benefit.”
Wei said the T2:ERG assay has the advantage of high specificity. When comparing a diagnosis of cancer vs. a benign biopsy, specificity was 88% (95% CI, 85%-91%) and sensitivity was 33% (95% CI, 28%-39%) with a cutoff greater than 100. With a cutoff greater than 200, specificity was 93% (95% CI, 90%-96%) and sensitivity was 23% (95% CI, 18%-28%).
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