Free PSA Accurate in Blacks

BALTIMORE—The 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 of urology.

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.

Subset Reanalysis

“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 higher risk.”

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 Women’s Hospital, and UCLA. ONI