April 26, 2007 — -- 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."
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."
He says the ECPA-2 test is 89 percent accurate at telling the difference between cancers that are confined to the prostate and those that have spread to other parts of the body -- an important distinction when it comes to deciding on aggressive treatment.
However, other urologists say it is too early to draw any conclusions about if and when the test will gain widespread acceptance.
Dr. Leonard G. Gomella, chairman of urology at Jefferson Medical College, said data is too limited to make promises to those who could benefit from the test.
"Lots of patients will want it long before it is even available experimentally," he said.
Other experts agree that hanging too much hope on the new test too soon could lead to disappointment for doctors and patients alike.
"If asked by a patient for a EPCA-2, I would need to respond that it is currently commercially unavailable and still experimental, although quite promising," said Dr. Richard E. Greenberg, chief of urologic oncology at Fox Chase Cancer Center.
"The preliminary data is encouraging but, again, we should not jump to conclusions about expanding into clinical practice until the test has been properly validated," said Dr. Ralph Hauke, associate professor of medicine at the University of Nebraska Medical Center.
Hauke said that until the test has proven itself through additional research and eventual clinical practice, it is unlikely to completely replace the PSA test. Instead, he said, the test will likely first be used as a supplement to help doctors weed out false positives -- ensuring that only those men who need biopsies get them.
According to Getzenberg, such an application could be an ideal entrance for the EPCA-2 test into clinical practice.
"We want to use it this way for a while before we make any claims that it could replace PSA," he said.
Approval of the test by the Food and Drug Administration -- a crucial step before it is incorporated into practice -- will entail more time for further study.
The company seeking FDA approval to market the test said it will take at least a year or two before the test becomes commercially available.
If there is any good news for men now, however, it is that other teams of researchers are currently devising a number of other tests based on other possible markers for prostate cancer.
"This is one of several tests to show promise," said Dr. Anthony Smith, professor and chief of urology at the University of New Mexico School of Medicine. "All of them have the potential to alter practice."
And Getzenberg said he is optimistic that clinical applications of the ECPA-2 test could be on the horizon.
"We're hoping that in the next 10 months to two years, this will be FDA-approved and we can get it out there," he said.
"There are a lot of men out there who are really very desperate for this kind of help to guide their decision making. I hope we can make this available soon."