The PSA blood test has been much maligned of late. Experts are concerned that blind screening of the general population leads to more harm than good. The apprehension is that many men are getting swept up into unnecessary radical treatment to treat innocuous forms of prostate cancer.
The problem with PSA testing used for screening is that elevated levels in the blood can result from a variety of causes including recent sex, strenuous exercise, an enlarged prostate gland or prostate cancer.
However, PSA testing is extremely useful for monitoring disease progression in men with known prostate cancer. Management of the disease is greatly simplified by this blood test. Rising PSA levels in the blood indicate that the cancer is growing. When levels are declining it serves as a clear signal that the cancer is responding to treatment.
PSA testing is particularly useful because it can be accurately measured in extremely small quantities, down to less than a billionth of a gram. Thus, cancer can be detected and tracked long before metastases become visible on a scan.
Just recently the FDA approved an enhanced PSA test called ProsVue. The test, manufactured by IRIS Molecular Diagnostics, can measure PSA levels below a trillionth of a gram. This new test has proven useful as a diagnostic marker for detecting the presence of residual prostate cancer after surgery.
Such a test has a practical application in men after surgery to help determine who is likely to develop a cancer relapse, i.e. to determine which men have residual microscopic cancer left behind after the operation. Only the individuals with microscopic disease are destined to relapse and will benefit by being treated with immediate radiation. Without the ProsVue, doctors have been giving radiation to everyone with positive surgical margins even though statistics show that only about half of the men being treated actually harbor residual microscopic cancer.
Bottom line: Previously published studies of standard ultrasensitive PSA assays used after surgery have shown some utility for predicting future cancer relapse. Therefore it is likely that ProsVue, which is substantially more accurate than existing PSA technology, will ultimately prove to be a useful and accurate test for predicting which men are at risk for a cancer relapse and are most likely to benefit from radiation.
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