New Prostate Cancer Test Shows Greater Accuracy

A new, more accurate test to detect prostate cancer may soon change the way doctors screen patients for the disease.

In practice the test would be similar to the one used today, which measures levels of a protein called protein-specific antigen, or PSA, in a patient's blood. However, the new test would also aim to detect levels of a protein called ECPA-2 in the blood.

The difference, according to a study in the current issue of the journal Urology, is that the new test has been shown to correctly identify which male patients did not have cancer 97 percent of the time, and which men did have prostate cancer 94 percent of the time.

By comparison, figures from the National Cancer Institute and others have shown the PSA test has specificity rate as low as 15 to 30 percent -- meaning that on average, for every four or six men who test positive, only one actually has prostate cancer.

"The PSA test is not very specific to prostate cancer, and that's its biggest issue," lead study researcher Robert H. Getzenberg, director of urology research at Johns Hopkins Medical Center told ABC News.

"For men with elevated PSA levels, only one in six who get biopsies today actually have prostate cancer," he explained. "This amounts to 1.3 million to 1.6 million men being biopsied to find the 230,000 or so who actually have prostate cancer."

Dr. Patrick Walsh, University Distinguished Service professor of urology at Johns Hopkins and author of "Dr. Patrick Walsh's Guide to Surviving Prostate Cancer," has called the new test "groundbreaking," saying: "As soon as it is approved, it may replace PSA."

However, the successful trials thus far may be only preliminary steps toward actual clinical use.

Dr. William Catalona, director of the Prostate Cancer Program at Northwestern University and one of the developers of the PSA test, said that though the results of studies thus far are "extraordinary," it is too early to say whether the new test will lead to a widespread change in current practice.

"I hold these investigators in high regard, but their preliminary results will have to be validated in a 'real world' prostate cancer screening setting before one is able to judge," he said.

"Their preliminary results seem to me to be too good to be true, but only further study will tell."

Urology Experts Debate Future Use

Though most researchers in the field agree that more studies need to be done before the test makes its debut in doctors' clinics, many say the results of this most recent study are exciting.

"This is a dynamite study with clear clinical implications," said Dr. Eric Klein, a urologist at Cleveland Clinic. "It is not ready for routine clinical use, but the results are exciting enough to do large-scale prospective trials to see how it performs. It has clear potential to affect clinical practice in deciding both who to biopsy and who to treat."

Moreover, Getzenberg explained, the new test also allows doctors to not only see whether prostate cancer is present, but also to determine whether a particular case is aggressive enough to warrant treatment or not.

"We're clearly overtreating a number of men who have prostate cancer that will never kill them," he said. "At the same time we're having a problem of under-treating some men."

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