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Prostate cancer urine test may one day reduce number of biopsies

The PSA test that men receive during a routine physical detects the presence of prostate-specific antigen, a protein produced by prostate cancer. • However, PSA levels can be raised by benign swelling of the prostate, which affects most men eventually, and by several medications, including ordinary, over-the-counter ibuprofen. • As a result, many men with elevated PSA don't have prostate cancer, which means they might receive an unnecessary biopsy — a minor but uncomfortable surgical procedure that harvests cells from the prostate for examination.

And if the biopsy shows the presence of indolent prostate cancer — the kind that grows so slowly that patients usually die of something else before their prostate cancer becomes life threatening — many men opt to have their prostate removed, which often leaves them with erectile dysfunction and some degree of incontinence.

But American men face a mere 3 percent chance of dying from prostate cancer, so the benefits of the PSA test, which reduces this small risk of death from prostate cancer by only a small amount, are easily offset by complications arising from unnecessary treatment. A 2009 article in the New England Journal of Medicine found that PSA screening was no better at reducing the death rate from prostate cancer than a traditional digital rectal exam. And an article in a recent issue of Annals of Clinical Biochemistry concluded that "it is unclear as to whether PSA screening of asymptomatic men for prostate cancer does more harm than good."

But help is on the way. Researchers have developed a urine test that can detect evidence of a genetic anomaly present in about half of men with prostate cancer. In addition, the test can help distinguish indolent prostate cancer from the more aggressive form. When combined with the PSA test, the new test could help reduce the 1 million prostate cancer biopsies performed every year in this country.

Researchers at the University of Michigan, working with Gen-Probe Inc. of San Diego, a maker of diagnostic products, analyzed the urine of 1,312 men who had elevated PSA levels, and who either had a prostate biopsy or surgery to remove the prostate. The urine carries evidence that a gene called TMPRSS2 has fused with another gene to produce a protein that accelerates the growth of prostate tumors. This fusion occurs in about half of all prostate cancers. The test also looks for evidence of prostate cancer antigen 3, or PCA3, which is often elevated in men with prostate cancer.

Based on the results of the urine test, the researchers divided the men into low-, intermediate- and high-risk categories, then looked at the type of cells removed from the men either through biopsy or surgery.

The urine test revealed that only 21 percent of the men in the low-risk group actually had cancer, compared with 43 percent in the intermediate-risk group, and 69 percent in the high-risk group. The urine test also revealed how aggressive the cancer was. Only 7 percent of the men in the low-risk group had an aggressive cancer, while 40 percent in the high-risk group did.

So when will this test be available?

"I could envision it in a lab by the end of this year or early 2012," said Dr. Arul Chinnaiyan, director of the Michigan Center for Translational Pathology and a professor of pathology at the University of Michigan Medical School. Chinnaiyan was the corresponding author of the paper, which appeared in the Aug. 3 issue of Science Translational Medicine. "I'm pushing for that to happen, but the ultimate decision is Gen-Probe's."

The new test should help distinguish various types of prostate cancer, and help in reducing unnecessary biopsies, said Dr. David Hernandez, assistant professor of urology at the University of South Florida.

"Prostate cancer is highly variable," Hernandez said. "This test may help us determine who has aggressive cancer and who has an indolent form. There's a lot of prostate cancer out there, but a lot of it doesn't need to be detected or treated.

"No one wants to overtreat prostate cancer, but no one wants to undertreat it either."

Tom Valeo writes frequently about health matters. He can be reached at tom.valeo@gmail.com.

Prostate cancer urine test may one day reduce number of biopsies 09/27/11 [Last modified: Tuesday, September 27, 2011 9:00pm]
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