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.
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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.
Approved in Europe, skeptics in United States
The FDA's European counterpart has already approved the test, he says. Catalona estimates that 18 percent of the 50 million American men who annually have their PSA levels tested fall into the diagnostic gray zone, so if the test is approved here, some 9 million men might be eligible to take it.
Not everyone shares Catalona's enthusiasm, however.
James L. Mohler, M.D., a urologist at the Roswell Park Cancer Institute and chair of the National Comprehensive Cancer Network's prostate cancer treatment guideline panel, says Catalona "basically improved the ability of the PSA to separate the benign from the cancer a little bit."
The study itself had some shortcomings, Mohler says.
Although Catalona "showed some differences that were interesting," the study should be repeated with more men who are studied over a longer period of time to see whether the Pro-PSA test really is more accurate.
Oliver Sartor, M.D., a urology professor and medical director of the Tulane University Cancer Center, agrees that the test is "better" at detecting who has cancer. But he cautions it's not ready for prime time, adding it may not help patients avoid biopsies. "Furthermore, the test clearly is not good enough to decide whether or not a cancer needs to be treated or not," he says.
"It moves us forward a little bit, but this isn't the answer to prostate cancer that we've all been looking for."
Michael Haederle is a freelance writer whose work has appeared in People, the New York Times and the Los Angeles Times.
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