BALTIMOREThe free prostate-specific antigen (PSA) test has
proved as accurate in revealing prostate cancer risk in black men as
in whites. It also shows that many African-American men could
be spared the expense and trauma of prostate biopsies, Alan W.
Partin, MD, PhD, co-leader of the research team, said in a news
release from Johns Hopkins University where Dr. Partin is professor
The data for the study were taken from the largest clinical trial to
evaluate the free PSA test, reported in 1998 in the Journal of the
American Medical Association. The free PSA test looks at the ratio of
free (unbound) PSA to the total PSA measurement.
The 773 men in the study, performed at seven US sites, were 50 to 75
years of age with a nonsuspicious digital rectal exam, a PSA result
between 4 and 10 ng/mL (the so-called diagnostic gray zone), and a
confirmed needle biopsy diagnosis. It found a 95% sensitivity for the
free PSA test in the group as a whole.
Because the trial was composed mostly of Caucasian men,
Dr. Partin said, we saw a need to reanalyze the data
specifically for the subset of African-Americans, who are at far
The new subset analysis compared results of the 647 white
participants and 79 black participants. In both races, free PSA
detected 95% of prostate cancers with a percent free PSA cutoff of
25%. Use of this cutoff could have avoided unnecessary biopsies in
20% of whites and 17% of blacks in the study (Urology 55:372-376,
2000). In both races, higher percent free PSA values indicated a
lower risk of cancer and also predicted favorable pathologic features
in radical prostatectomy specimens.
The study, funded by a research grant from Hybritech Incorporated
(San Diego) used the Hybritech free PSA assay.
The study sites, in addition to Johns Hopkins, were Washington
University, Baylor College of Medicine, University of Washington,
Seattle, Loyola University (Maywood, Ill), Harvard and Brigham and
Womens Hospital, and UCLA. ONI