Three Gene Urine Test for Prostate Cancer May Eliminate Invasive Biopsies

By LabMedica International staff writers
Posted on 11 Apr 2016

A real-time PCR assay that measures levels of RNA generated by three prostate cancer-linked genes may someday replace classical detection methods for this disease and eliminate the need for invasive biopsies.

In a recent study, investigators at Columbia University (New York, NY, USA) used the Exosome Diagnostics (Cambridge, MA, USA) ExoDxTM Prostate(IntelliScore) assay to detect RNA from three genes (ERG, PCA3, and SPDEF) that have been linked to the development and progression of prostate cancer. The RNA was encapsulated in lipid membrane-coated structures called exosomes that were excreted by cancer cells into urine.

Image: Micrograph of a needle biopsy specimen of prostate adenocarcinoma, acinar type, the most common type of prostate cancer (Photo courtesy of Wikimedia Commons).

In the study, prostate biopsy results from 774 men with PSA (prostate specific antigen) levels between two and 10 were compared to a composite score that was based on results of the urine test plus other risk factors, including PSA level, age, race, and family history of the disease.

Results revealed that the assay had correctly identified 92% of men with high-grade cancer. However, the test also predicted high-grade cancer in 66% of men whose biopsies revealed low-grade or no cancer. In clinical practice, use of the test would have spared 27% of men from having an unnecessary prostate biopsy.

“The test has the potential to be a significant improvement over PSA alone in distinguishing between low- and high-grade prostate cancers, especially in the PSA gray zone patient. It could reduce hundreds of thousands of invasive biopsies each year. Given the pain and risks associated with performing a prostate biopsy, that is not a trivial thing,” said first author Dr. James McKiernan, professor of urology at Columbia University. "In addition, the test is the only urine-based assay that does not require a digital rectal exam prior to collection and is easily integrated in the clinic environment."

The study was published in the March 31, 2016, online edition of the journal JAMA Oncology.

Related Links:
Columbia University
Exosome Diagnostics