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Medical Pike
"Free" PSA Prostate cancer test works as well for black men, study
shows
March 6, 2000. - The "free" PSA test to predict prostate cancer risk appears to offer
African-American men a much-needed, improved accuracy in detecting the disease.
A review of data from a recent nationwide trial of the free prostate specific antigen test (fPSA) a
variation on the traditional PSA test shows the new test proves as accurate in revealing cancer
risk in African American men as it is in Caucasians.
"It also shows that many African-American men could be spared the expense and trauma of
prostate biopsies," says Johns Hopkins urologist Alan W. Partin, M.D., Ph.D., co-leader of the
research team. "Nearly 75 percent of the prostate biopsies that both black and white men get are
unnecessary," says Partin. A report on the study at Johns Hopkins and six other U.S. medical centers appears in the March
issue of the journal Urology.
The fPSA, a more sensitive test for cancer risk than the standard PSA test men get as part of
routine physicals, won Food and Drug Administration approval two years ago, based on a national
trial of 773 men who had both tests as well as prostate biopsies. This earlier trial showed that
fPSA detected 95 percent of the cancers.
It also reduced unnecessary prostate biopsies that men would have routinely after the standard
PSA test.
Men of a variety of races took part in this original trial, which compared the two tests as detectors of
prostate cancer. "But because the trial was composed mostly of Caucasian men," Partin says, "we
saw a need to re-analyze the data specifically for the subset of African-Americans, who are at far
higher risk."
The new analysis shows no significant differences exist between blacks and whites in the
performance of the fPSA test.
Since FDA approval, the fPSA is becoming a follow-up test for men whose PSA falls in a
"diagnostic gray zone" of moderately elevated levels--4 /to 10 ng/ml. The risk of prostate cancer
in this group is 25 percent in Caucasians and 30 to 50 percent in African-American men. Prior to
development of the free PSA test, men in the "gray zone" had to undergo biopsies, often
repeated. Prostate biopsies are expensive around $1,000 and may be painful or psychologically
traumatic, says Partin.
"Because early detection is currently our best hope against prostate cancer," says Partin, "it's
crucial that we can rely on effective screening tools like the free and total PSA tests regardless of
the patient's race."
"African-American men have the highest rate of prostate cancer in the world,' says Partin. It's
approximately one-third greater than for white males. They also have higher PSA values when
the cancer is diagnosed. "No one understands the precise reason for this," he adds, "though
theories abound. It's probably a combination of biological and environmental factors."
PSA is an enzyme made by all prostate cells and normally secreted into semen. Both cancer and a
number of benign conditions can change the architecture of the prostate gland so the enzyme
"gets out the back door" and into the bloodstream. Once there, PSA can exist in two forms -- one
that's free-floating and another that's bound to proteins. The standard PSA test measures both
forms. The free PSA test looks at the ratio of the free form to the total.
Having a higher amount of free PSA is linked with a lower risk of
prostate cancer.
The study was funded by a grant from Hybritech Incorporated, San Diego, Calif. Other researchers in the study were Patrick C. Walsh, M.D., professor and director of the Department of Urology at Johns Hopkins, William J. Catalona and Kathy Naughton, of Washington University in St. Louis, Kevin M. Slawin and Peter Scardino of the Baylor College of Medicine, Houston, Michael K. Brawer and Paul H. Lange of the University of Washington, Seattle, Robert C. Flanigan of Loyola University, Maywood, Ill., Anup Patel and Jean B. deKernion of UCLA, Jerome P. Richie of Harvard, and Paula C. Southwick, Kathleen G. Loveland, Robert E. Parson and Gail H. Gasior of Hybritech Incorporated, San Diego.
Neither of the Hopkins researchers hold any financial interest in Hybritech or its subsidiaries. Alan W. Partin is the editor of Urology.
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