Prostate Cancer PSA Testing Faster, More Specific

For more than a decade, testing the amount of prostate specific antigen (PSA) in the blood has been used as a 'front-line' tool in screening patients for prostate cancer. Recent advances in PSA testing include automated machines that can determine PSA levels in about 15 minutes, reducing by a week or more the waiting time for results, and refinements in how those levels are interpreted.

In general, according to William See, MD, Medical College of Wisconsin Professor and Chairman of Urology, PSA testing and increased public awareness have gone hand-in-hand in greatly reducing the number of men who are found to have prostate cancer that has already metastasized (spread to other areas of the body). Before PSA testing became widespread, he said, 50% of men with prostate cancer presented with disease spread throughout the body, while today fewer than 5% present with advanced disease.

"PSA is really an extremely useful tool in the management of prostate cancer in two regards," said Dr. See. "At the first level, it is the best tool currently available to screen patients for prostate cancer. The level of PSA roughly correlates with the probability of a patient harboring prostate cancer, and so it's an important discriminator for patients at very low risk versus patients at moderate to high risk. That piece of information, together with the individual patient's risk-taking profile, allows them to make a decision as to whether or not they want to pursue additional testing.

"Screening is important, but there's also an equally useful role for PSA in the management of patients with established prostate cancer. That's really where the rapid PSA has been extraordinarily valuable. After treatment for prostate cancer, PSA should either go to zero or go to and remain at very low levels. So patients come in to our office knowing that they have prostate cancer, knowing that their PSA is going to determine whether or not they're cancer-free or whether their cancer has come back."

Rapid Results Ease Worries
Froedtert Hospital was the first in Wisconsin to install an "in-house" PSA machine. "Historically," said Dr. See, "we'd draw the PSA and then there'd be an interval of angst during which the patient would be struggling with the question of 'am I going to make it or am I going to die?' because that's their view as it relates to their cancer recurrence. What we do with rapid PSA is contract considerably the time interval over which that angst occurs.

"Patients come into our clinic, they get their blood drawn, fifteen minutes later they get their lab results back, and we move on. In the vast majority of them they're doing fine, and they know it, and they know it right away. So there's not this worry lasting anywhere from two days to a week about what their PSA is going to show."

The US Food and Drug Administration has approved use of the "15-minute" machines for patients who have already been diagnosed with prostate cancer and undergone some treatment. Approval to use the machines for advance screening is pending as the FDA determines whether the rapid PSA test is as accurate as tests performed using traditional laboratory techniques.

Dr. See observed that in certain circumstances it can be vital for the patient that the test can be used not only for screening but for diagnosis. "Let's say someone comes in who has an abnormal digital rectal examination or some voiding complaints related to potential prostate problems," he says. "In a diagnostic sense we'll check that patient's PSA, and quickly."

The primary function of the prostate gland, which is highly prone to cancer, is to secrete the fluid that moves sperm forward during ejaculation. About 30,000 deaths in the US result from prostate cancer each year, and the American Cancer Society estimates that there will be more than 220,000 new cases diagnosed in 2004.

A protein measured by the PSA test goes up as prostate cancer develops. However, PSA levels also rise when the prostate becomes inflamed by colonoscopy, bladder infection or recent sexual activity. Given the variety of causes for increased PSA, including the fact that more PSA is produced as a natural function of aging, Dr. See noted that it is important that PSA tests continue to be made more precise and sensitive to increase their value in diagnosis and treatment of prostate cancer.

"Scoring" Refinements Continue
"PSA doesn't mean anything in terms of the actual substance," said Dr. See. "Your PSA could be 10,000 and the PSA per se doesn't hurt you. But what it tells us is how much prostate cancer is there. And so, in the post-treatment setting, progressive rises in your PSA tell us that there's more prostate cancer; or, as an example, if the PSA comes back after a given therapy, that your disease is recurrent and progressive.

"Conversely, decreases in your PSA following some treatments are good. They indicate a good response. It's a little bit like blood cell counts in patients with leukemia, as an example. It gives an index of what their disease is doing. But in the case of prostate cancer, (PSA provides such an indicator) probably far more specifically and far more sensitively than virtually any other test available on the market. PSA continues to be an important component of many clinical trials that we do here at the Medical College."

Until recently, a PSA level higher than 4.0 nanograms per milliliter of blood was considered cause for concern in very general terms. Now many practitioners are age-adjusting PSA scores so that the "acceptable" level of PSA starts lower and rises as the patient ages. "Nobody in prostate cancer management is resting on their laurels," said Dr. See. "Investigators both in this country and around the world are striving to identify markers with greater specificity but equal sensitivity for prostate cancer. As an example, just this past year for men under 60, we in the urologic community went back and looked at the original analysis that was used to define the cut points for normal versus abnormal PSA.

"What was discovered was that there were some assumptions made in the original testing that skewed the analysis a little bit. When we corrected for those assumptions, we in fact found that for men under 60 perhaps the better balance between specificity and sensitivity is no longer for a PSA cut point of 4.0 but a PSA cut point of 2.5.

"What we've learned is that PSA is not static over the course of a man's life. It should be low when you're young and it gets higher as you age. The older you are the higher your PSA is, and that's probably not due to age but related to benign prostate volume, the fact that benign prostate tissue makes PSA as well as cancerous prostate tissue and that, as we age, the one thing that gets bigger is our prostate."

Dan Ullrich
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.