'Promising' New Test to Detect Prostate Cancer
Researchers Hope It May One Day Replace PSA Test
Sept. 21, 2005 -- A new blood test for prostate cancer is a "promising
technique," write the test's inventors in The New England Journal of
The test just requires a routine blood draw. But it isn't ready for use yet,
note Arul Chinnaiyan, MD, PhD, and colleagues.
If successful in other studies, the new test could enhance and perhaps
eventually replace PSA blood tests, states Chinnaiyan, in a
PSA (prostate specific antigen) is made by the prostate. High PSA levels can
indicate prostate cancer. But they can also signal noncancerous conditions,
such as an enlarged prostate, which limits the use of this test as a method of
screening for prostate cancer.
"Initially, we envision this new test could be used as a supplement to
PSA," states Chinnaiyan, a pathology professor at the University of
"A physician might suggest a patient with an elevated PSA have this test
before a biopsy to better determine whether it's a cancerous or benign
condition. In the future, I think this could replace PSA," he
Many men who get biopsies after PSA tests turn out not to have prostate
Reliance on PSA for the detection of early prostate cancer is still
unsatisfactory, especially because many times (around 80% of the time) elevated
levels of the protein (PSA) turn out not to be from prostate cancer, write the
Building a Better Test
First, Chinnaiyan's team studied a large library of prostate cancer tissues.
They found 22 proteins that they thought would make a good prostate cancer
blood test. Researchers have found that patients with cancer produce antibodies
against proteins found on tumors.
Next, they looked for those antibodies in blood from men with and without
All of the prostate cancer patients had had biopsies showing localized
prostate cancer. That means their cancer hadn't spread beyond the
prostate. The patients were also at least 40 years old and hadn't had prostate
cancer therapy before.
The new blood test usually worked in detecting only those men who had
prostate cancer, the study shows. But two out of 70 healthy men and seven out
of 69 men with prostate cancer were misclassified.
Finally, the scientists tested 128 more blood samples, 60 of which came from
prostate cancer patients.
Once again, the test's results were mainly right. The test accurately
identified prostate cancer 81% of the time and correctly showed no cancer 88%
of the time, the researchers report.
It's not yet known if the test will work in men with other prostate
conditions, autoimmune system problems, or other diseases, write the