Urine Test Might Help Predict Prostate Cancer Risk
WEDNESDAY Aug. 3, 2011 -- A new urine test might help doctors detect prostate cancer and better evaluate a patient's treatment options, researchers say.
"This is a tool that men and their physician can use to help them decide whether it's appropriate to get a biopsy now or delay that decision," said lead researcher Dr. Scott Tomlins, a pathology resident at the University of Michigan Health System.
The test looks for two genetic markers associated with prostate cancer. The first, called TMPRSS2:ERG, is caused by two genes changing places and fusing together; it is thought to cause prostate cancer. Since the gene fusion is only seen in about half of cancer patients, the test also looks for another marker, called PCA3.
"We are exploiting some new bio-markers to try to refine the PSA [prostate-specific antigen] test," Tomlins said.
The PSA test can indicate prostate cancer, but it is unreliable, often producing false positives and false negatives, Tomlins said. "You can have low PSA and have cancer, or high PSA and not have cancer," he said.
The two genetic markers may be more reliable indicators of prostate cancer, he said. One of them, TMPRSS2:ERG, is only seen in cancer, he added.
Together, they can be used "to stratify men into saying, 'You have a high chance of having cancer, and you should get a biopsy now, or if you are in a lower risk group you have a much lower risk of cancer and perhaps you could delay the biopsy,'" Tomlins said.
However, Tomlins cautioned that the test is not perfect. "It's hard to recommend that someone not get a biopsy, because there is always a chance you are going to miss a cancer that doesn't have either of these two markers," he said.
For the study, published in the Aug. 3 issue of Science Translational Medicine, Tomlins' team studied urine samples from 1,312 men who had high PSA levels and had had a prostate biopsy or surgery to remove the prostate.
The researchers specifically looked for the two markers and used them to slot the men into high-, intermediate- or low-risk groups for prostate cancer. They then compared their results with the results from biopsies, which are done with a needle in a physician's office for detection of any cancer cells.
Based on the biopsies, cancer was found in 21 percent of the men in the low-risk group, in 43 percent of the intermediate-risk group and in 69 percent of the high-risk group.
The researchers said the findings of the urine tests correlated with tumor size and the cancer's aggressiveness. In the low-risk group, only 7 percent had aggressive cancer, compared with 40 percent of the men classified as high-risk, they found.
One limitation of the study is that most patients were Caucasian, so further studies are needed to see whether the findings extend to all men, the researchers noted.
Although not yet available to the public, the test soon will be offered at the University of Michigan, Tomlins said.
The test is licensed to Gen-Probe, a San Diego maker of genetically based diagnostic tests. Mike Watt, a company spokesman, said the test is still in the early stages of development and has not been submitted to the U.S. Food and Drug Administration for approval. The company has no firm idea of the test's cost should it be approved, Watt added.
Study funding was supported in part by Gen Probe, and the University of Michigan and Brigham and Womens Hospital have obtained a patent on the detection of ETS gene fusion in prostate cancer, in which four co-authors are listed as co-inventors.
A prostate cancer expert, Dr. Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston, said the test is "a step forward, but we still have a ways to go."
"On average the risk is higher in people with both markers and lowest in people who have neither, but that's on average," D'Amico said.
If a patient has indications of an aggressive prostate cancer, the test can add more to that diagnosis, D'Amico said. But for men who potentially have cancer, a low-risk determination based on this test shouldn't preclude biopsy, he said.
"It adds fuel to the fire when you suspect something bad, but I don't think it takes you out of the woods when these markers are not present," D'Amico said.
For more information on prostate cancer, visit the American Cancer Society.
Posted: August 2011