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SUMMARY
It is too early to routinely use free PSA for prostate cancer
screening
The free form of PSA represents an average of 30% of total PSA.
The free PSA level, in relation to total PSA, is expressed as a per -
centage (of free PSA).
The percentage of free PSA appears to be relatively independent
of benign prostatic hypertrophy, but it is markedly and signifi -
cantly decreased in the case of prostate cancer and acute pros -
tatitis.
A cut-off value for the percentage of free PSA combined with
a cut-off value for total PSA can decrease the number of biop -
sies indicated for the detection of prostate cancer. This
a p p roach avoids 20 to 30% of useless biopsies (specificity),
but is accompanied by a 5 to 10% reduction of the number of
cancers detected (sensitivity of 90 to 95%) compared to the
use of total PSA alone. This 5 to 10% risk of missing a cancer
of significant volume in a man under the age of 65 years
explains why the use of free PSA to guide prostatic biopsies is
not routinely recommended. Despite the promising performan -
ce of the percentage of free PSA to improve the indication for
p rostatic biopsies, the methodology of the studies performed to
evaluate this test is not sufficient to validate their conclusions.
The percentage of free PSA can be prescribed as a second-line
test by the urologist, following a first series of negative biop -
sies in a man with a high clinical and laboratory suspicion of
p rostatic cancer, in order to propose a second series of biop -
sies after three months or to define the frequency of clinical
and laboratory surv e i l l a n c e .
While waiting for the results of prospective studies in the scree -
ning setting, recommendations concerning the use of PSA by
general practitioners, who are the first to order this test in the
context of screening, can be formulated as follows:
The value of free PSA assay for first-line cancer screening has
not been validated. A consensus has not been reached concer -
ning the use of free PSA as an indication for biopsies and the fre -
quency of assays. Total PSA assay (cut-off value: 4 ng/ml)
remains the reference laboratory test for screening and indica -
tion of biopsies. A lower normal cut-off value (between 2 and 4
ng/ml) is currently under evaluation.
Key Words : Prostate cancer, PSA, free PSA, screening, diagno -
sis.
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A. Villers, D. Chautard, Progrès en Urologie (2000), 10, 618-621