They say such a test could help identify those who need aggressive treatment and might one day lead to the development of new therapies.
"There are metabolites that might be useful in predicting aggressiveness of prostate cancer," said lead researcher Dr. Arul Chinnaiyan, director of the Michigan Center for Translational Pathology and a professor of pathology and urology.
"Metabolites, similar to genes and proteins, should also be measured in understanding cancer," he said. "They have been under-appreciated relative to genes being profiled in cancer. This approach could be extended to other cancers."
However, before a urine test involving metabolites could become standard medical practice, it would have to be tested in animals and then in people through clinical trials, Chinnaiyan said.
The findings were expected to be published in the Feb. 12 issue of Nature.
For the study, Chinnaiyan's group analyzed 1,126 metabolites from 262 tissue, blood and urine samples taken from men with early, advanced and metastatic prostate cancer. From these samples, the researchers identified 10 metabolites that frequently appeared with prostate cancer and especially with advanced prostate cancer.
One of the 10 metabolites, called sarcosine, was the most indicative of advanced prostate cancer, the researchers found. Sarcosine levels were elevated in 79 percent of the samples from men with metastatic cancer (cancer that has spread) and in 42 percent of the samples from men with early stage disease, the researchers found.
No trace of sarcosine was found in samples from men who did not have prostate cancer, the researchers noted.
According to the report, sarcosine was a better indicator of advanced prostate cancer than the current marker for the disease, prostate specific antigen (PSA).
And, sarcosine's involvement in the invasiveness of the cancer suggests that blocking it might be a target for future drug development, Chinnaiyan said.
The findings are preliminary, though, Chinnaiyan noted, and it would be years before a test or treatment based on the metabolite could be available. Ideally, he said, researchers would like to find other metabolites associated with prostate cancer that would help predict the course of the disease with even more precision.
More than 186,000 people in the United States will be diagnosed this year with prostate cancer, and almost 29,000 will die from the disease, according to the American Cancer Society.
Michael M. Shen, a professor of medicine, genetics and development at Columbia University College of Physicians and Surgeons in New York City, and co-author of an accompanying journal article, said that the report advances the use of metabolites in understanding cancer.
"The hope is that this approach will ultimately yield a clinical application," Shen said. "For example, one could screen urine from men and not only diagnose prostate cancer but have information that would be useful for cancer prognosis."
However, that goal is a long way off, he said. "The importance of the paper is that there is a new methodology that has not been pursued extensively before, which in combination with existing approaches may yield advances in cancer diagnosis and prognosis," he said.
Dr. Margaret K. Offermann, the deputy national vice president for research at the American Cancer Society, stressed that studies are needed to see if the approach could be used in patients.
"This is not a perfect test," Offermann said. "It is not perfectively predictive of when someone is going to have prostate cancer and when that cancer is going to misbehave, but it may help in combination with PSA," she said.
And it could be a new target for treatment, she said. "Potentially, by blocking the formation of sarcosine or related compounds, it may actually help in the treatment," she explained.
The American Cancer Society has more on prostate cancer.
SOURCES: Arul Chinnaiyan, M.D., Ph.D., director, Michigan Center for Translational Pathology, professor of pathology and urology, University of Michigan Medical School, Ann Arbor, Mich.; Michael M. Shen, Ph.D., professor, medicine and genetics and development, Columbia University College of Physicians and Surgeons, New York City; Margaret K. Offermann, M.D., Ph.D., deputy national vice president for research, American Cancer Society; Feb. 12, 2009, Nature
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