August 4, 2011 in Nation/World

New prostate test promising

Urine screen could help eliminate false positives
Shari Roan Los Angeles Times
 

Prostate cancer screening may become significantly better with the use of a urine test, according to a new study.

Prostate cancer screening is currently based on a blood test to detect PSA – prostate-specific antigen. But that test often produces false positives and leads to unnecessary biopsies. More than a million men in the U.S. undergo a prostate biopsy each year, and fewer than half of the patients actually have prostate cancer. The test is also thought to lead to over-treatment of prostate cancer. Studies show that an estimated 23 percent to 44 percent of all prostate tumors found through PSA testing would never have caused any symptoms.

The new test appears to be better at detecting prostate cancer and determining which cancers will be aggressive.

“Many more men have elevated PSA than actually have cancer, but it can be difficult to determine this without a biopsy,” the senior author of the study, Arul Chinnaiyan, said in a news release. “This test will help in this regard. The hope is that this test could be an intermediate step before getting a biopsy.”

Researchers at the University of Michigan looked at urine samples of 1,312 men who had suspicious PSA levels and had gone on to have a biopsy or surgery to remove the prostate. The urine samples were examined for a marker indicating prostate cancer, a fusion of two genes called TMPRSS2:ERG. This gene fusion is found in about half of all cases of prostate cancer. Researchers also looked for another marker, a prostate cancer antigen called PCA3.

The two urine markers together were able to reliably predict whether the patient had prostate cancer and suggested which men were at higher risk of aggressive disease. The researchers ranked the men into low-risk, medium-risk and high-risk groups based on the urine-test scores. The biopsies showed 21 percent of the low-risk men had cancer compared to 43 percent of the medium-risk group and 69 percent of the high-risk group. Seven percent of the men in the low-risk group had aggressive cancer compared to 40 percent in the high-risk group.

Most of the patients were white, so further studies are needed to see if the test is as accurate in other racial and ethnic groups. Moreover, future studies should examine how well the test works in men who have not had PSA tests first.

The paper was published Wednesday in the journal Science Translational Medicine.

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