The Urology Center Glossary terms

PSA (prostate specific antigen):

Prostate specific antigen (PSA) is a protein enzyme found in the prostate, in urine and in the blood stream of men with prostate glands. As the name implies, PSA is prostate specific but not specific for prostate cancer. Testing prostate and urinary PSA has not proven useful. However, studies have shown that bloodstream PSA is often elevated in men with prostate cancer. Doctors have more experience with the use of this blood test than with the use of any other cancer detecting blood test. PSA is used both for prostate cancer screening and prostate cancer follow-up testing.

... a man with an elevated PSA is twice as likely to have cancer as a woman with an abnormal mammogram.

PSA is an effective screening tool for prostate cancer. In fact, a man with an elevated PSA is twice as likely to have cancer as a woman with an abnormal mammogram. On average, PSA allows the detection of prostate cancer some 4-5 years before the cancer could otherwise have been detected. When men are tested at the recommended ages for cancer screening, PSA testing often allows the detection of prostate cancer while the cancer is still confined to the prostate gland. At this early stage, prostate cancer is curable. Without PSA testing, however, prostate cancer is often detected only after it has spread beyond the confines of the prostate, making cure of the cancer practically impossible.

Many urology specialists believe that normal PSA values depend on the age of the patient. Commonly used abnormal PSA ranges are as follows: (1) men in their 40s -- > 2., (2) men in their 50s -- > 3.5, (3) men 60 or older -- < 4.0. Some say that men 70 or older may have PSA values up to 6.5. Other experts feel that no man should have a serum PSA > 2.5. Obviously, there is no exact range of normal that perfectly discriminates between a man who has prostate cancer and a man who does not.

... a better way of using PSA to screen for prostate cancer is ... PSA velocity.

Conceivably a better way of using PSA to screen for prostate cancer is monitoring of repeated PSA blood tests perhaps every 6, 12 or 24 months (depending on the clinical situation) so that new PSA values may be compared with established PSA values for the same patient over time. This form of assessment is sometimes called PSA velocity. Determination of the rate of increase in serum PSA may be an even more useful means of early detection of prostate cancer. In fact, when men undergo prostate cancer screening including PSA testing in successive years, detected cancers are usually smaller and more amenable to treatment for cure. Certainly, PSA velocity has been shown to detect cancer, even in patients with normal PSA values of less than 2.5!

Another effective method for PSA prostate cancer screening is the determination of a portion of total blood PSA that his not protein-bound. This so-called "free" PSA ratio ideally should be greater than 25 percent in men with total PSA values between 4 and 10. Determination of free PSA ratio and may be best suited for men with elevated total PSA values having undergone prior negative prostate biopsies. In such cases, an abnormal free PSA ratio may guide the urologist to perform additional biopsies.

PSA is not a perfect test for the detection of prostate cancer. There are no perfect tests in medicine. Some men with elevated PSA values may not have prostate cancer. Likewise, some men with normal PSA values actually harbor prostate cancer. Approximately 25 percent of men who are diagnosed with prostate cancer have PSA levels in the normal range. In these cases, prostate cancer is detected by digital rectal examination of the prostate, by removal of a portion of the prostate during surgery for prostate enlargement, by monitoring of PSA velocity or by other methods.

An even more established method of PSA utilization is for the follow-up in patients after treatment for prostate cancer. PSA levels guide clinical decision-making after every form of treatment. In general, PSA levels accurately reflect the status of the cancer. Additional methods of cancer monitoring include bone and Prostascint scanning for metastatic disease.

(Please visit our Benign Prostate Enlargement Center of Excellence and Prostate Cancer Center of Excellence for additional information.)