New Test for Prostate Cancer Proposed

In a large-scale clinical trial, a new version of the PSA test used to screen prostate cancer was better able to detect an aggressive form of the disease, as well as substantially reduce false positives.

See also: When to treat prostate cancer.

William J. Catalona, M.D., considered the father of the original PSA test and director of the clinical prostate cancer program at Northwestern University Feinberg School of Medicine, says the new test will identify more life-threatening prostate cancers and reduce needless biopsies in men age 50 and older to rule out cancer.

Other experts caution the test doesn't give information valuable enough to prevent unnecessary treatment.

The test for total prostate specific antigen (PSA) often returns false-positive results, and even after a biopsy confirms cancer, many men have surgery or radiation to treat slow-growing tumors that are unlikely to kill them.

The new screening test weighs a specific PSA subform called Pro-PSA, which is higher in patients who have prostate cancer, against total PSA and free-circulating PSA, which may be elevated in patients with benign prostate enlargement instead of cancer.

PSA by the numbers

Prostate cancer is unlikely when total PSA is less than 2 nanograms per milliliter, and very likely when greater than 10 ng/ml, Catalona says, so the 2-to-10 range is a "gray area" where biopsies are usually ordered — yet only about a quarter of those men will be diagnosed with cancer.

In a new paper published in the Journal of Urology, Catalona and 16 colleagues administered the Pro-PSA test to nearly 900 men from 10 sites, including Northwestern, whose total PSA fell in the 2-to-10 range. The new test did a better job than the earlier version of predicting who had cancer, they found. A higher score on the Pro-PSA also meant a man was more likely to have an aggressive form of cancer.

Medical manufacturer Beckman Coulter, which developed the Pro-PSA test, has asked the Food and Drug Administration to approve it for men age 50 or older whose total PSA values are between 2 and 10 ng/ml. Beckman Coulter, for which Catalona serves as an unpaid consultant, supported the costs of conducting the research.

When deciding whether a man should get a biopsy right away or just monitor his total PSA levels, "the Pro-PSA test would provide a more accurate discriminator of whether he has cancer … so it's better than anything that's out there," Catalona says.

Next: Test may not help patients avoid biopsies. >>