PSA is a protein circulating in the blood given off by normal prostate cells as well as prostate cancer cells. This blood test is often used as a screening test to look for men who may have prostate cancer. While it is far from perfect in determining who has and does not have prostate cancer, it is an extremely useful tool. Interpretation of results has to include assessing the patient’s age, gland size and a variety of other factors. It is extremely useful to have a PSA history when assessing the implications of a PSA number. I therefore ask patients to gather all of their old test results so that we can look at their current number in light of what it has been in the past.
% Free and Total PSA is a ratio of the free or unattached PSA to all of the PSA (total) in the blood. This test works inversely. A high number suggests a lower risk of prostate cancer, while a lower number put the patient in a higher risk category. “Free PSA” is the PSA that is floating freely in the blood vs. PSA that is attached to other proteins in the blood.
PSA -3 is a newer test that has been shown to help select which men are at risk of having prostate cancer even though they have had a negative biopsy.
PSA is even more useful as a “tumor marker.” For men who have had treatment of prostate cancer, following their PSA after surgery or radiation is a great way of watching for recurrences. A biochemical failure is when the PSA starts consistently rising after cancer treatment. Fortunately, there are usually many years between a bio-chemical failure and the onset of symptoms from a tumor.