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What’s New In Testing For
Prostate Cancer?: “Upm3, A New Molecular Urine Test For The Detection Of
Prostate Cancer.” (Oct 2004)
The “rate of positive
biopsies in men with PSA levels between 2.5 and 4.0 ng/mL is 20% to 23%”
and “over half these are clinically organ confined aggressive
cancers”. The overall accuracy for cancer detection using tPSA in men
with PSA > 2.5 is 43%, leaving ample room for improvement. In
early evaluation the new uPM3 urine test has shown an 81% overall
detection accuracy.
The performance of the uPM3
test was evaluated at five institutions in 517 men and reported in
Urology, August 2004. The test is a “molecular cytology” that
identifies cancer cells expressed in the first 20 - 30 cc. after a 15 - 20
second “attentive” prostatic massage. The specific molecular targets
are “PSA mRNA as a marker of prostate cells and mRNA expressed by the
PCA3 gene, “one of the most prostate-cancer specific genes described so
far, with over expression in 95% of cancers tested and a median 66-fold
upregulation compared to adjacent non-neoplastic tissue. In this early
evaluation 86% of men produced assessable specimens. Subsequent to the
testing the men underwent prostate biopsies, and the correlation of the
uPM3 results, the total serum PSA, and the outcome of the biopsy was the
subject of the report.
The most promising and
potentially clinically useful information arises from the evaluation of
the group of 95 men whose PSA levels were < 4.0 ng/mL, where the new
test had a 74% sensitivity and a 91% specificity. The authors suggest that
the test “may be particularly attractive in identifying those at high
risk of cancer in the large population of men with a PSA level between 2.5
and 4 ng/mL” and may provide guidance in the decision to rebiopsy men
whose initial biopsies were negative. Among 91 men whose initial biopsy
was negative, the uPM3 test had a 74% sensitivity and a 87% specificity
for identifying those men who were positive on rebiopsy. Additionally, a
positive uPM3 test may be a better indicator of risk than “prostate
biopsy features considered to [indicate] high risk such as HGPIN or atypia.”
Bottom
Line:
If confirmed in further evaluation, the uPM3 test, with its capacity to
identify a very few malignant cells in urine, may offer “an overall
accuracy twofold greater than the tPSA assay.”
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