A URINE test can help doctors better spot prostate cancer than either the current blood test or a rectal exam alone, US researchers reported recently.
They said Gen-Probe’s Progensa PCA3 test caught about half the actual cases of prostate cancer in men who had abnormal PSA levels or digital rectal exams, and had about a 20% “false positive” rate.
“That’s pretty good, actually,” said Dr David Crawford of the University of Colorado School of Medicine, who helped lead the study.
Trying to diagnose prostate cancer is one of the most maddening tasks a doctor has to do.
The prostate is a walnut-shaped gland that produces semen. Digital rectal exams can tell a specialist that it is getting bigger, but that happens with normal ageing as well.
A blood test for prostate specific antigen or PSA shows when PSA rises, but PSA goes up with either cancer or just normal enlargement of the prostate – or even if the gland is inflamed, such as from an infection.
Biopsies are difficult and painful to do and may take a portion of healthy prostate, missing any tumours entirely. And prostate tumours can grow slowly.
A study last year estimated that more than one million men in the US alone had been needlessly treated for prostate tumours that likely would never have killed them.
The Progensa test looks for a genetic material called PCA3. It is a string of RNA that does not appear to have any function but that is overexpressed, or overactive, in prostate cancer.
Lightly touching the prostate can cause its release and it can then be detected in the urine using the test.
Crawford and colleagues tested Progensa in about 1,900 men who had high PSA readings, an abnormal digital rectal exam or both and who were scheduled to have biopsies.
“It reflects on the aggressiveness of the cancer,” Crawford said. “If you had no cancer, your PCA3 was at 25 or 20. If you had precursors such as high grade PIN (prostatic intraepithelial neoplasia), your score was about 38 to 40 and men who had cancer scored about 50 to 55.”
The test indicated that 78% of the men had cancer and actually did. This compares to just 21% for PSA alone, the researchers told a meeting of the American Urological Association in San Francisco.
“If the PCA3 is abnormal, above about 35, you have got an 80% chance of having cancer,” Crawford said. – Reuters