After non-melanoma skin cancer, prostate cancer is the most-common cancer afflicting men in the United States. In fact, according to the American Cancer Society, more than 200,000 U.S. men will be diagnosed with the cancer this year. A new urine test could give men some hope in fighting the cancer by enabling earlier diagnosis. According to researchers at the University of Michigan, the test can be used to complement screening for elevated prostate-specific antigen (PSA) and could provide some men with an alternative to needle biopsy. In addition, the test could identify men that have the highest risk for clinically significant prostate cancer.
The new test works by diagnosing a genetic anomaly, present in roughly half of all prostate cancers, in which two genes swap places and fuse together. This gene fusion, which is known as TMPRSS2:ERG, is thought to cause prostate cancer by overruling the cells’ mechanism that limits cell growth. In studies of prostate tissues, gene fusion nearly always indicated cancer.
To further improve the accuracy of the test, the researchers included another marker known as PCA3. “Testing for TMPRSS2:ERG and PCA3 significantly improves the ability to predict whether a man has prostate cancer,” says Scott Tomlins, M.D., Ph.D., 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.”
From the announcement:
The researchers looked at urine samples from 1,312 men at three academic medical centers and seven community-based hospitals. The men all had elevated PSA levels and had gone on to receive either a biopsy or prostatectomy, surgery to remove their prostates. The researchers evaluated the urine samples for TMPRSS2:ERG and PCA3 and stratified patients into low, intermediate and high scores, indicating their risk of cancer. They then compared this to biopsy results.
Biopsies indicated cancer in 21 percent of men from the low-score group, 43 percent in the intermediate group and 69 percent in the high group. Further, 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 percent of men in the low-score group had an aggressive tumor while 40 percent of those in the high-score group did.
“Many more men have elevated PSA than actually have cancer but it can be difficult to determine this without biopsy. This test will help in this regard. The hope is that this test could be an intermediate step before getting a biopsy,” says senior study author Arul Chinnaiyan, M.D., Ph.D., director of the Michigan Center for Translational Pathology and S.P. Hicks Professor of Pathology at the U-M Medical School. Chinnaiyan is also a Howard Hughes Medical Institute researcher.
Prostate biopsies are done with a needle in an office setting, but they do pose some discomfort and risk to the patient. In addition, a biopsy can offer an incomplete picture since urologists are testing the prostate as a whole, rather than a specific lesion.
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., which has licensed the technology.
Press release: Urine test shows prostate cancer risk, U-M study finds