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Oak Brook Urology 2425 West 22nd Street, Suite 216, Oak Brook IL 60523 |
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800-770-2791 630-9904244 |
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| PROSTATE SPECIFIC ANTIGEN (PSA) EXPLANATION
PSA stands for Prostate Specific Antigen and is a blood test that is used to screen for the presence of prostate cancer. The prostate is the gland, found only in men, which is located between the urinary bladder and the urethra (the urinary channel that runs through the penis). The prostate's function is to make seminal fluid or semen that is ejaculated during intercourse. Note that sperm is made in the testicles and is only a small fraction of the seminal fluid. Antigen is a medical or biological term for a substance, usually a protein, that stimulates the body to make antibodies. PSA is, therefore, a protein found in the blood that is unique or specific for the prostate. No other human tissue or body part can make PSA except for the prostate. The PSA levels can be measured in an individual's serum and with this information we are able to screen for prostate cancer. WHY USE PSA TO SCREEN FOR PROSTATE CANCER? The routine use of PSA testing along with digital rectal examination (DRE) of the prostate has dramatically improved our ability to find prostate cancer earlier, and possibly at a more curable stage, than ever before. Controversy exists as to whether earlier diagnosis leads to longer survival, but it is our hope that PSA testing will lead to lives being saved because of earlier treatment. WHAT CAUSES THE PSA TO RISE? PSA is only present in men. PSA is present in all normal prostate tissue. The normal prostate cell holds onto most of the PSA and lets very little leak into the blood stream. The small amount that leaks out is the PSA that is measured by the blood test. Prostate cancer cells actually have less PSA in each cell, but the cancer cell tends to leak more PSA into the bloodstream, hence the reason for measuring the PSA levels. Knowing this fact, we have come up with a range of expected values in patients with a normal prostate gland. We believe that the PSA value should be less than 4.0. This number is somewhat arbitrary but reflects our feelings that most men (95% or so) with normal prostate glands have a PSA value of 4.0 or less (see below about age-specific normal values!). The catch is the word 'normal'. Almost any condition that affects the prostate can make the PSA rise. In addition, not all patients with prostate cancer have an elevated PSA. Twenty percent of diagnosed prostate cancers occur in men whose PSA values are normal! The most common non-cancerous cause of elevated PSA levels is benign prostate hyperplasia, more commonly known as BPH. As men age, particularly after age 50, the prostate enlarges or grows normally. The most common symptom with BPH is difficulty urinating. About 80% of men will develop some aspect of BPH in their lifetime. BPH is NOT cancer, nor will it lead to cancer, but BPH may cause a false elevation of PSA values. Another common cause of false elevation of PSA value is prostatitis. Prostatitis simply means inflammation of the prostate. Prostatitis is very common and usually causes symptoms similar to a bladder infection (burning, frequency and urgency to urinate). However, many men with prostatitis have no symptoms. The inflammation from prostatitis causes PSA to leak into the bloodstream and causes the PSA level to be higher than normal. Even a simple rectal exam can cause the PSA to rise somewhat. Ejaculation has been shown to cause an increase in the PSA level in some men for about 48 hours. If possible, the patient should not ejaculate for 48 hours before a PSA test. If ejaculation has occurred and the PSA is elevated, a repeat test might be necessary. What this means is that PSA is NOT a cancer measurement, and that an elevated PSA does NOT mean you have cancer. The ONLY test that will determine the presence of cancer with certainty is a biopsy of the prostate. DOES AGE HAVE ANYTHING TO DO WITH PSA LEVELS? Recent studies have suggested that the 4.0 cut-off
level may be too high for younger men and too low for older men. Most
of the studies for which we have long term evaluation have used the
4.0 level. Some researchers now recommend the following levels, although
more time is needed to assure that these levels are more accurate
than just the 4.0 value. WHAT DO WE DO WITH AN ELEVATED PSA LEVEL? FIRST TIME MEASUREMENT OF PSA
Remember, PSA is merely a predictor of the possibility of prostate cancer. A normal PSA does not mean that you do not have prostate cancer. It means that you have lower risk of having a prostate cancer. Conversely, an elevated PSA does not mean you have cancer either. It just means that you are at greater risk than someone whose PSA is lower. Probability of Prostate Cancer based on test results Standard PSA Level Probability of Prostate Ca PSA of 4* or less - If your PSA level has been measured
for the first time and is less than 4, we recommend repeating the
test on a yearly basis. PSA greater than 4 - If your PSA is greater than 10, we recommend a diagnostic ultrasound of your prostate done through the rectum (TransRectal Ultrasound or TRUS) with biopsies of the prostate simultaneously. If the ultrasound shows no suspicious areas, then systematic biopsies of the entire prostate are usually taken. If the ultrasound shows suspicious areas, then biopsies of the areas, along with systematic biopsies, need to be done. Other ways to look at PSA values (PSA Density)
IF YOU'VE HAD PREVIOUS MEASUREMENTS OF PSA
When we have the luxury of previous PSA values, we look at numbers a little bit differently. The PSA level will almost always rise in the face of a cancer that is growing. Any PSA level that is rising is suspicious. As mentioned earlier, the high PSA level may NOT mean that cancer is present. For example, a male with a stable PSA of 8 over a three year period (8,8,8) is probably at less risk than a male with a PSA of 2, 4, and 6 over the same time frame, even though the value 8 is above all the values of the second patient! The second patient's rising levels suggest growth and has to be considered suspicious for cancer. If the first patient with repeating 8 values had a negative biopsy when first discovered, then there may be no need to repeat the biopsies. If his levels jumped to 10 or 15 for no apparent reason, then repeat ultrasound and biopsies would be indicated. Recent studies suggest that either a 20% rise or a measurable rise of 0.75 in PSA in one year should prompt a closer look and possibly an ultrasound and biopsy. Some physicians use the term PSA Velocity or PSAV to describe the change in PSA values over time 'Free PSA' and Complexed PSA
Another way of evaluating the same information is the total amount of 'complexed PSA'. The normal value for 'complexed PSA' is about 3.75 ug/ml and probably offers little benefit over total PSA. WHAT'S NEW Another problem, yet to be solved, is the comparison of assays for PSA, free PSA and complexed PSA. Countless companies are offering PSA test kits. Are the different kits, many of which use different chemical reactions giving the same PSA levels? The differences are probably not significant but having the PSA testing repeated at the same laboratory may be a benefit. Unfortunately, many labs change PSA testing kits without notice. FOLLOW-UP We also recognize that many groups feel that PSA
screening should not be done routinely. To date, no evidence exists
that routine PSA screening saves lives and many believe that the treatment
of prostate cancer might cause more harm than help. Patients need
to be aware of the risks of screening and not screening. Please ask
if you have any questions. Copyright 1999 Dialog Medical, Inc. All rights reserved
www.dialogmedical.com
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