Prostate Specific Antigen

PSA or Prostate specific antigen is a protein produced by prostate gland cells. In recent years, the PSA test which measures the amount of PSA in the bloodstream, has been used to screen for the presence of prostate cancer. The use of the PSA test as a screening procedure is actually controversial.

PSA is in the category of biological marker or tumor marker.

The PSA test is also used to follow men after treatment for prostate cancer. A rising PSA after treatment may indicate a recurrence of the prostate cancer.

It is normal for men to have a certain amount of PSA in their bloodstream. The PSA test checks for elevation of the PSA.

Not all elevations of the PSA are due to cancer. In fact, benign prostatic conditions such as benign prostatic hyperplasia (or BPH) and prostatitis can also cause a rise in the PSA. To actually definitely diagnose prostate cancer, a doctor must do other tests such as a prostate gland biopsy. As noted above, the use of the PSA test as a screening test for prostate cancer is actually controversial so that different doctors may have different recommendations.

It is known that certain groups are at a higher risk for prostate cancer. These higher risk groups include:

*Older Men. Nearly 70% of prostae cancer occur in men 65 years of age and older.

*Men with a positive family history. Men who have a father or brother with prostate cancer have a greater chance of developing prostate cancer.

*Certain ethnic groups. African American males have the highest rate of prostate cancer. Asian and Native American males have the lowest rates.

*There is some evidence that a diet higher in fat, especially animal fat, may increase the risk of prostate cancer.

The PSA Test Is Controversial

As noted above, the use of the PSA test as a screening test for prostate cancer is actually controversial so that different doctors may have different recommendations.

The reason for the controversy is that the data is unclear as to whether the PSA test actually increases survival. Plus, it is not clear whether or not the benefits of the PSA test outweigh the downsides in terms of the risks of the diagnostic procedures following a postive PSA, and the side effects of treatment if a prostate cancer is found and treatment is decided upon.

Limitations of The PSA Test

*Although the PSA test may help detect prostate cancer, it may not increase a patient's survival. An elevated PSA test sometimes results in the detection of a slowly-growing prostate cancer which is unlikely to reduce a man's life. 

Also, the PSA test may detect an aggressive or fast growing prostate cancer which has already spread. In this case, the PSA may not result in increased survival.

*The PSA test may result in what are known as false positive tests. A false positive test in this case implies that the PSA test is positive but, after investigation, there is no cancer present. Actually, most men with an elevated PSA turn out not to actually have cancer. In fact, only 25-30% of patients who have a biopsy on the basis of an elevated PSA turn out to have cancer.

*The PSA test may result in what are known as false negative tests. In these cases, the PSA test is negative although prostate cancer is actually present. 

In order to make the PSA test better in terms of distinguishing between benign prostatic conditions and prostate cancer, a number of methods are being studied.

These methods include:

*PSA velocity. This refers to the change in PSA levels over time. A significant rise in the PSA may raise the suspicion of prostate cancer.

*Age-Adjusted PSA. Since PSA levels rise with increasing age, studies are being done to determine the concerning levels for each age group.

*The form of PSA. PSA circulates in the blood in two forms - either free or attached. It seems that there may be more free PSA in the benign prostate conditions while there is more attached PSA with prostate cancer.

*The relationship of the level of PSA to the size of the prostate gland. This is referred to the PSA density.