By Will Boggs, MD

NEW YORK, Mar 21 (Reuters Health) - A screening test used on a sample of urine can find cells that have precancerous changes in DNA or proteins, researchers report. The test may be able to detect early changes that could lead to bladder cancer, the fifth most common cancer in the Western world.

While there are screening tests that are used to detect recurrent tumors in people already diagnosed with bladder cancer, none of the tests are approved in the US for detecting or diagnosing bladder cancer.

Because of the need for a better screening method, Dr. George Hemstreet III, from University of Oklahoma Health Sciences Center in Oklahoma City, and associates looked at three cell "markers"--specific changes in cell DNA or proteins--to see if they predicted bladder cancer. The researchers looked for the markers in nearly 1,800 Chinese workers exposed to benzidine, a chemical commonly associated with the development of such cancers.

Over a 6-year period, 28 of the individuals developed cancer of the bladder, the authors report, a cancer rate nearly triple that of workers not exposed to the chemical.

Two of the three markers proved especially useful in predicting bladder cancer in these workers, the report indicates. One test--called DNA ploidy--looks for abnormal numbers of chromosomes in the cells passed in the urine.

The second test looked for a protein often associated with bladder cancer. This marker, known as antigen p300, was second best at estimating risk, the researchers note, but it was the most accurate overall test for detecting cancer of the bladder.

Combined, these markers could detect changes 33 months before cancer was diagnosed in the medium-risk group and 15 months before cancer was diagnosed in the high-risk group, the results indicate. Workers who had either DNA ploidy or antigen p300 were 20 times as likely to develop bladder cancer as workers with neither markers.

"The biology of cancer and the technology available today can cost effectively be used to define individuals at risk for cancer," Hemstreet told Reuters Health.

One of the biggest challenges, he said, is to close the gap between what scientists have discovered and what doctors are able to test for--and this requires expensive, often lengthy clinical testing.

This challenge is not likely to diminish. According to a related editorial by Dr. Adi Gazdar from The University of Texas Southwestern Medical Center in Dallas and Dr. Bogdan Czerniak from M.D. Anderson Cancer Center in Houston, Texas, "investigators are currently testing methods for the detection of literally thousands of (markers) in clinical samples. These methods remain to be applied and tested in large-scale, population-based studies."

Related MEDLINEplus Pages:

• Bladder Cancer