Prostate Specific Antigen (PSA)


Introduction.

As Prostate Cancer becomes an increasingly important disease around the world and in Malaysia, there has been a rising urgency to try to detect this disease in its earlier treatable stages. Since the discovery of PSA in the mid 1980s, it has revolutionized the detection of Prostate Cancer as well as help in the monitoring of the effects of treatment.


What is PSA?

Prostate Specific Antigen (PSA) is a small protein that is produced exclusively by the prostate gland. It is found in high amounts in the semen and is generally confined there. Its function is in the liquefaction of semen. The normal lining of the prostate gland prevents it from entering the blood stream to any significant degree and it is only the small amounts that leak out into the blood (serum) that becomes detectable in normal men. This is the amount that is measured in the blood test.


What is the normal PSA range?

The normal range of PSA in blood testing has often been quoted as 0 - 4 nanogram per ml. There is however more recent evidence that suggest that the normal range should be age specific and as such, the upper range can be extended upwards in more elderly men. Conversely, the younger man may then be expected to have an upper range that is correspondingly lower.


What does an elevated PSA mean?

An elevated PSA does NOT equate to Prostate Cancer. As mentioned, PSA is produced by cells of the prostate gland. Therefore, a big prostate gland (Benign Prostatic Hyperplasia or BPH) can cause an elevated PSA even if it is not cancerous. Any infection/inflammation of the prostate gland (Prostatitis) which causes a breach in the lining cell layer of the prostate gland and allows for 'leakage’ of PSA into the blood stream can also cause an increase in the PSA value as will any urinary tract instrumentation or even prostate massage.

The main concern however, is whether any specific elevation of PSA indicates the presence of Prostate Cancer.


Elevated PSA and Prostate Cancer.

Prostate cancer cells actually have less PSA in each cell, but the cancer cell tends to leak more PSA into the blood stream. Hence it is expected that the PSA levels are higher in men with Prostate Cancer and the higher the value the higher the possibility. This is especially of concern if there are no other overt causes for the elevation of the PSA.

Usually the more overt causes are more easily identified and it is often the marginally elevated PSA values that cause difficult differentiation between a benign enlargement and prostate cancer.


What to do with an elevated PSA?

An elevated PSA does NOT mean one has Prostate Cancer. The only test that will determine the presence of cancer is a biopsy of the prostate. Assuming a digital rectal examination of the prostate has been normal, the degree of elevation of the PSA helps in determining whether such a biopsy is indicated. (Incidentally, all abnormal digital rectal examinations should lead to biopsy regardless of the PSA level.)

Therefore an elevated PSA should be evaluated more thoroughly by a Urologist. The latter will most probably arrange for a Transrectal Ultrasound of the prostate gland besides the rectal examination and based on that and the PSA level, decide whether a biopsy of the prostate gland is necessary.


Should one have his PSA routinely checked?

At this time, there is no formal recommendation for this to be done and major medical institutions around the world have not arrived at a consensus. There is certainly no doubt that men at high risk including men with a family history of prostate cancer should have their prostates screened for cancer and this would include having the PSA checked from age 45. It is still controversial whether asymptomatic men who are otherwise not at risk should have their prostates screened from age 50.

For the present moment, it is probably wise to have a discussion with a urologist before undertaking such a testing so as to be aware of the implications of both a normal and abnormal result.

Present ongoing studies around the world will hopefully give us more definite answers when they are completed in the coming years.