A new twist on the standard way 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, known as 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 Alan W. Partin, professor of urology in the School of Medicine and 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.
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 reanalyze 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 ng/ml 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, Partin says.
"Because early detection is currently our best hope against prostate cancer," Partin says, "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," Partin says. 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.
"For some reason," says Partin, "having a higher amount of free PSA is linked with a lower risk of prostate cancer."
Among the researchers was Patrick C. Walsh, professor/director of the Department of Urology, who discussed the findings at a March 16 press conference attended by Gov. Parris Glendening (See the related story in this issue, "Researchers Develop Noninvasive Screening Test for Cancer").