Gene Fusion Test Assists Early Prostate Cancer Detection

The test looks for a genetic anomaly that occurs in about half of all prostate cancers in which two genes change places and fuse together. This gene fusion, TMPRSS2:ERG, is believed to cause prostate cancer. However, because the gene fusion is present only half the time, scientists included another marker, PCA3. The combination was more predictive of cancer than either marker alone.

The test supplements an elevated prostate specific antigen (PSA) screening result, and could help some men delay or avoid a needle biopsy while revealing men at highest risk for clinically significant prostate cancer.

A study from the University of Michigan (U-M) Comprehensive Cancer Center (UMCCC; Ann Arbor, MI, USA) and the Michigan Center for Translational Pathology (MCTP; Ann Arbor, MI, USA), which evaluated the test was published on August 3, 2011, in the journal Science Translational Medicine.

Urine samples were examined from 1,312 men at three academic medical centers and seven community-based hospitals. The men all had elevated PSA levels and had received either a biopsy or prostatectomy. The urine samples were evaluated for TMPRSS2:ERG and PCA3 and patients were stratified into low, intermediate, and high scores, with regard to their risk of cancer. This was then compared to biopsy results.

Biopsies indicated cancer in 21% of men from the low-score group, 43% in the intermediate group, and 69% in the high group. In addition, the urine test scores correlated with how aggressive the cancer was based on tumor size and Gleason score, a measure of how abnormal the cells look. Only 7% of men in the low-score group had an aggressive tumor while 40% of those in the high-score group did.

The combined TMPRSS2:ERG and PCA3 test is not yet available as a prostate cancer screening tool. The Michigan Center for Translational Pathology is working with Gen-Probe Inc. (San Diego, CA, USA), which licensed the technology, and hopes to offer it to U-M patients within the year. U-M currently offers PCA3 screening alone as follow-up to elevated PSA.

“Testing for TMPRSS2:ERG and PCA3 significantly improves the ability to predict whether a man has prostate cancer,” said lead author Scott Tomlins, MD, PhD, a pathology resident at the U-M Health System. “We think this is going to be a tool to help men with elevated PSA decide if they need a biopsy or if they can delay having a biopsy and follow their PSA and urine TMPRSS2:ERG and PCA3.”

Senior study author Arul Chinnaiyan, MD, PhD, director of the Michigan Center for Translational Pathology and S.P. Hicks Professor of Pathology at the U-M Medical School added, “The hope is that this test could be an intermediate step before getting a biopsy.”

Related Links:
University of Michigan (U-M) Comprehensive Cancer Center
Michigan Center for Translational Pathology
Gen-Probe Inc.