Researchers believe they have found a compound produced by aggressive prostate tumors and hope they can use it to design a urine test to detect the most dangerous tumors, they said Monday.

Prostate cancer, which is found in 780,000 men every year globally and kills 250,000, can be very slow-growing. While common, it does not always require immediate treatment.

One difficulty is identifying the patients who need the most careful monitoring after surgery or radiation therapy to destroy the tumor.

Scott Tomlins and colleagues at the University of Michigan Health System looked at 1,800 prostate tumors to try to identify the unique “signature” of an aggressive type of prostate cancer found in about 10 percent of patients.

A gene called SPINK1 was over-expressed, or over-active, in about 44 percent of cases of prostate cancer, they reported in the journal Cancer Cell. Their findings suggested that cancer was twice as likely to come back after surgery among men with SPINK1-related prostate cancers.

Tumors recur after surgery in between 25 percent and 40 percent of men, the researchers said.

Because the gene can be detected in the urine, without any invasive procedures, a test could be developed to complement urine tests currently used to detect some prostate cancers, said Dr. Arul Chinnaiyan, who oversaw the research.

Tests include a blood test that looks for prostate-specific antigen (PSA), a protein produced only by prostate cells. Prostate tumors produce extra levels of PSA, but so does a prostate that is simply enlarging with age, making the test imprecise. Doctors also use digital rectal examination to detect irregularities.

San Diego-based Gen-Probe Inc. has a urine test to screen for a protein called PCA3, although it is not approved in the United States.

The University of Michigan has filed for a patent on SPINK1 as a “biomarker” for prostate cancer and licensed rights to Gen-Probe.

The researchers said they do not know precisely how SPINK1 is involved in cancer and will continue to investigate.

WASHINGTON (Reuters)