Researchers find protein pattern to increase accuracy of prostate cancer detection

<br>WASHINGTON (AP) _ A pattern of protein markers in the blood may be used to sharpen the diagnosis of prostate cancer and to eliminate unneeded biopsies, researchers say. <br><br>Using a new system that

Wednesday, October 16th 2002, 12:00 am

By: News On 6

WASHINGTON (AP) _ A pattern of protein markers in the blood may be used to sharpen the diagnosis of prostate cancer and to eliminate unneeded biopsies, researchers say.

Using a new system that analyzes traces of protein, it may be possible eventually to use a single drop of blood to determine to a high degree of accuracy if a man has prostate cancer, researchers say in a study appearing Wednesday in the Journal of the National Cancer Institute.

``With further study, this has the potential to revolutionize the diagnosis and treatment of prostate cancer,'' said Dr. David Ornstein, a prostate cancer specialist at the University of North Carolina in Chapel Hill and co-author of the study. ``This could help significantly reduce unnecessary biopsies.''

Men over 50 are currently being screened routinely for prostate abnormalities with a blood test for the prostate specific antigen, or PSA. In most practices, men with PSA readings between 4 and 10 are routinely biopsied to determine if they have prostate cancer.

Still, an estimated 70 percent to 80 percent of men with abnormal PSAs don't have cancer; they have a benign condition that prompts the midrange PSA reading.

``The critical clinical question in prostate cancer is who should get biopsies when their PSA is in this intermediate range,'' said Emanuel Petricoin, a researcher at the Food and Drug Administration and first author of the study. Thousands of men have biopsies that would not be needed if doctors could determine with high accuracy from a blood test whether cancer was present, he said.

A system that precisely measures a pattern of proteins in the blood could be that test, said Petricoin.

In the study, Petricoin said, researchers first analyzed blood from men with prostate cancer and from men without the disease. Using a computer that could discern patterns, the researchers developed a program that could identify minute differences in the types and quantities of proteins in the blood.

Using this information, the researchers then did a blinded analysis of blood from men, some with cancer and some without it. They asked the computer to identify the blood samples with protein patterns matching those of men with prostate cancer and to find those whose proteins did not indicate cancer.

``It got 95 percent of the cancer cases and 100 percent of those with a benign condition correct,'' Petricoin said of the computer-driven diagnostic. ``It learned to distinguish between those with cancer and the healthy.''

Petricoin said the prostate cancer diagnostic must undergo more extensive experiments before it is ready for general use, but a test for ovarian cancer, also using protein patterns in the blood, is being readied for clinical trials. That test detects an ovarian cancer at a very early stage using proteins from a blood sample, he said.

Dr. Jonathan Epstein, a specialist in the pathology of prostate cancer at Johns Hopkins University in Baltimore, said a blood test that could positively identify those with prostate cancer would ``definitely be of value,'' but he cautioned that such a system would have to be very accurate.

``It would have to have a very high sensitivity so it would not miss many cancers,'' said Epstein. ``But if it could reliably say that 40 to 50 percent of the men (with midrange PSAs) have no cancer, and there's virtually no risk of the test being wrong in patients who otherwise would get biopsies, then it would be a tremendous help.''