New Blood Test for Prostate Cancer

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.

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 te 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."

By Daniel DeNoon
Reviewed by Louise Chang
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