New Blood Test for Prostate Cancer
Experimental Test Detects Prostate Cancer, Tells Whether It Is Spreading
EPCA-2 Test Beats PSA
Nobody is entirely happy with the current PSA test for prostate cancer. A man without prostate cancer can have high PSA levels. A man with advanced prostate cancer may have very low PSA levels.
Getzenberg's team tried out the EPCA-2 test on blood samples from several different groups of people. Some were known to have early prostate cancer or late prostate cancer, and some had other kinds of cancer. Some had enlarged prostates, but not cancer. Some were women, who have no prostate gland. And some were healthy men with normal PSA levels.
Both in terms of detecting cancer when it was actually there (sensitivity), and in terms of not detecting cancer when it wasn't actually there (specificity), the EPCA-2 test beat the PSA test.
More importantly, it beat the PSA test in predicting whether prostate cancer already had spread outside the prostate gland. When that has happened, standard treatments for prostate cancer -- radical prostatectomy (surgery to remove the prostate) and brachytherapy (tiny radioactive seeds implanted in the prostate) -- fail to cure.
"I predict that within the next year, this test is going to be widely used to find the guy who has prostate cancer and who, if he got radical prostatectomy, would relapse very quickly," Brawley tells WebMD. "It is going to say to this guy, 'Skip the unnecessary surgery and get pelvic radiation and hormone treatment now.'"
Getzenberg says it will be at least two years before the test is "out on the street" with FDA approval. All of the experts who spoke to WebMD agree that large-scale screening tests will be needed before it's known exactly how well the test works.
"What we really need to know is how this test behaves in all comers -- when we don't already know whether the men being tested have prostate cancer," Palapattu says. "It would also be important to identify men with high risk of prostate cancer vs. low risk of prostate cancer, and to test men after prostate surgery to see whether it can predict cancer recurrence."
When -- and if -- the EPCA-2 test is approved, men will still need better prostate cancer tests.
"At least a third, maybe two-thirds of guys with localized disease have cancer that will never leave the prostate and never bother them," Brawley says. "This new test is not going to help those guys who get treated for prostate cancer but shouldn't. I hope there will be help for these men soon."