New Blood Test for Prostate Cancer

April 26, 2007 -- An experimental blood test for prostate cancer seems to work better than the current PSA test -- and can tell whether the cancer is spreading.

The new test looks for a protein called EPCA-2 -- or early prostate cancer antigen 2. Unlike the PSA (prostate-specific antigen) protein on which the current PSA test is based, this protein isn't found in normal prostate cells. Instead, EPCA-2 occurs in relatively large amounts only in prostate cancer cells.

The test is being developed by Robert H. Getzenberg, PhD, director of urology research at Johns Hopkins University's Brady Urological Institute. Getzenberg began the work while still at the University of Pittsburgh; the test has been licensed to the Seattle biotech firm Onconome Inc.

"We wanted to find something that really identified people with prostate cancer and not people with enlarged or infected prostates," Getzenberg tells WebMD. "This is as close to cancer specific as we could find. We found it is very unique. It is 97% specific, meaning that if you test positive there's only a 3% chance you don't have prostate cancer."

Getzenberg has a financial interest in the test. But experts who do not stand to gain from the test agree that it has enormous potential.

Otis Brawley, MD, chief of the solid tumor service at Emory University's Winship Cancer Institute, calls the test "important" and predicts it will be widely used.

Charles A. Coltman Jr., MD, associate chairman for cancer control and prevention at San Antonio's Southwest Oncology Group, calls the findings "striking" and "remarkable," although he warns that the test has been tried out on only a small number of patients.

Ganesh Palapattu, MD, assistant professor of urology at the University of Rochester, agrees that more studies must be done. But he tells WebMD that the test is a big step toward the "Holy Grail of prostate cancer detection: not so much identifying men with prostate cancer, but identifying men with prostate cancer who have aggressive disease."

"This not only helps tell whether you have prostate cancer, but what kind of prostate cancer you have," Getzenberg says.

Getzenberg and colleagues report early studies of the EPCA-2 test in the April issue of the journal Urology.

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.