PSA stands for Prostate Specific Antigen. It is a protein that is uniquely produced by the male Prostate gland. It is called an "antigen" because its presence in the bloodstream can be detected by antibodies (antibodies "trap" antigens).

The Prostate gland (not the "prostrate" gland) is a small, soft, globular piece of tissue in the lower pelvis of men. Through it runs the urethra -- the last "pipe" of the urine system that goes from the bladder to the penis. The Prostate gland provides lubrication for the urethra in order to keep it from blocking up and to keep bacteria from entering the bladder.

All men (after puberty) have detectable PSA. This is because the Prostate manufactures this protein and small amounts of it leak into the bloodstream. Any abnormal tissue growth of the Prostate gland will result in the increased production of PSA. Thus, an elevated blood level of PSA indicates an abnormal amount of Prostate tissue -- it does not indicate what the abnormality is !!

One of the most common conditions in older men is Benign Prostatic Hypertrophy (BPH). This is simply an enlargement of the Prostate gland that would have no consequence except that it tends to block the normal flow of urine and BPH may cause confusion with the very serious condition known as Cancer of the Prostate (CA Prostate or Prostatic CA).

Two of the differences between BPH and CA Prostate are:

CA may cause hard, irregular areas in the Prostate while BPH is usually softer and more generalized in its growth. These abnormalities may be detected by a physician who can actually feel the Prostate gland through the soft front wall of the rectal cavity. This is known as the Digital Rectal Examination (DRE).  

The PSA level in BPH does not go as high as it does in CA. The normal PSA is less than 4.5, and values from 4.5 to 10 may mean either condition. BPH generally does not cause the PSA to rise over 20. The PSA in BPH tends to remain constant but the PSA in Cancer may rise at a regular rate (it also may not).

Thus, if the DRE and the PSA are both normal, it is unlikely that BPH or CA Prostate are present. It must be noted however, that very early CA (tiny foci or a lesion on the front of the gland) may not be detectable. If either the DRE or the PSA is abnormal then a biopsy must be undertaken to make a clear diagnosis. This is done by inserting a needle into the gland and pulling out a tiny sliver of tissue. The needle is inserted under the guidance of an ultrasound image of the gland. (This is somewhat like radar and the doctor looks for areas of the Prostate where the tissue appears "different" from normal). The sliver of tissue is then examined under a microscope by a Pathologist who looks for Cancer cells.

If the diagnosis of Cancer is made there are a variety of different treatments that can be instituted. This selection is made using knowledge of the size of the cancer lesion, whether it has spread through the wall of the gland (or beyond), the type of cancer cell that is present, the patient's age and physical condition, and the patient's own choice.

Whatever the therapy, the PSA is generally used to monitor how well the therapy it is doing. Obviously, the lower the value -- the more successful the treatment. However, the progression of cancer of the Prostate is hard to predict and it varies from patient to patient. Some cancers are very slow growing and would not cause a problem for the patient even if left without any treatment at all while others are rapidly progressive in spite of all forms of therapy. Unfortunately, there is no certain way to make such a prediction.

When monitoring the PSA it must be realized that it won’t be possible to have exactly  the same value every time.  The value may normally change up or down by 0.5 and occasionally more.  The important information is a steady trend shown by three tests or more.

The Medical Services Plan in British Columbia will pay for PSA if it is done to follow treatment or in diagnosis when there is a strong suspicion of Cancer. If the PSA is being ordered as part of a general examination, the provincial medical insurance will not pay for it. This is due to the fact that "screening" with PSA tests has not been conclusively demonstrated to be medically necessary. Most patients are quite willing to pay the fee for a PSA.

A modification of the PSA is the “Free PSA”.  This refers to the fact that some PSA molecules are attached to other molecules while other PSA molecules are unattached (free).  The Free PSA test can be used to help distinguish whether a PSA increase is due to BPH or Cancer.  It is of no use when the total PSA is under 4.0 or above 10.  The test is certainly not 100% in this distinction and must not be totally relied upon.