A urine test to distinguish men with different risks of developing prostate cancer is being investigated by scientists.

Current screening for prostate cancer uses a blood test to measure a protein called prostate specific antigen, or PSA, that may signal that something is awry. But a man's PSA level can be high for other reasons. Even a biopsy after a high PSA isn't definitive.

So the PSA may help detect cancer early. Or it may detect a cancer that is slow-growing and never poses a threat and does not need aggressive therapy. Making that distinction is a key goal in prostate cancer research.

Now investigators writing in Wednesday's online issue of the journal Science Translational Medicine are reporting what they hope is a step in that direction.

The findings "may provide an opportunity to help men and their physicians make more informed decisions about early detection, biopsy, and management of prostate cancer in the context of elevated serum PSA," lead author Dr. Scott Tomlins, a pathology resident at the University of Michigan Health System and his co-authors concluded.

Genetic anomaly

The proposed urine test looks for a genetic anomaly that occurs in about half of all prostate cancer when two genes change place and fuse together, the researchers said.

In the study, researchers analyzed urine samples collected from 623 men referred for needle biopsy at three academic centres, including 213 in Laval, Que., as well as 471 men who went to community clinics throughout the U.S.

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 the two biomarkers and grouped subjects into low, intermediate and high scores by cancer risk. They then compared this to biopsy results.

Biopsies resulted in a cancer diagnosis in 21 per cent, 43 per cent, and 69 per cent of men in the lowest, intermediate, and highest groups.

The scientists reported that their urine test findings corresponded to the biopsy results.

The combined test is not available as a prostate cancer screening tool. It would need to pass further testing for safety and effectiveness before it gains regulatory approval for sale.

A limitation of the study is that most the participants were Caucasian, and more research will be needed to determine whether the findings apply to all men, the study's authors said.

The University of Michigan and Brigham and Women's Hospital have been issued a patent on the discovery.

Gen-Probe Inc., the Early Detection Research Network, U.S. National Institutes of Health, Prostate Cancer Foundation, Burroughs Wellcome Fund, Doris Duke Foundation, and Howard Hughes Medical Institute funded the research.