PSA

PSA stands for prostate-specific antigen. This is a specific protein (enzyme) which is produced by the prostate and secreted into the semen. This makes the semen thinner, making the sperm more mobile. It is normal for very small amounts of PSA to enter the bloodstream.

PSA levels are measured in nanograms per millilitre (ng/ml) of blood. Measuring the PSA level allows the doctor to see whether it is within the normal range or is raised. There are many reasons why the PSA level may be raised, including inflammation, benign enlargement of the prostate, recent prostate surgery, but also prostate cancer. A raised PSA level does not therefore necessarily mean prostate cancer, it merely indicates that something unusual is going on in the prostate.

Why do a PSA test?

In addition to standard screening tests, urologists will often recommend a PSA test if:

• there is a specific reason to suspect the patient may have prostate cancer
• the patient has symptoms such as problems passing water that could be caused by prostate cancer
• the patient requires regular monitoring or follow-up

The PSA test – reasons why PSA levels may be raised

Prostate cancer is not the only reason why PSA levels may be raised. PSA levels can also be raised if the prostate is inflamed (prostatitis) or enlarged (benign prostatic hyperplasia). Pressure on the prostate, such as from riding a bicycle or after ejaculation, can also increase PSA levels. Blood for a PSA test should therefore always be taken before carrying out a digital rectal examination or ultrasound scan.

Other factors affecting the prostate, such as severe constipation, prostate massage, acute urinary retention, the presence of an indwelling urinary catheter, recent endoscopy of the urethra and bladder (urethrocystoscopy), colonoscopy or biopsy of the prostate can also increase PSA levels.

Is a biopsy always required after an abnormal PSA test?

Medical opinion varies on how high the PSA needs to be before a biopsy (when a tissue sample is taken) should be carried out to enable an accurate diagnosis to be made. The German Urology Association has therefore come to the consensus that a biopsy should be carried out when the following criteria are met:

• the PSA level is more than 4 nanograms per millilitre (ng/ml) of blood and has been verified by making a second measurement
• repeat measurements show that the PSA value is continuing to rise

If these criteria are met, your urologist will discuss with you how best to proceed and will explain the procedure for and potential consequences of having a biopsy.

Why is there so much controversy in the press about the PSA test?

There have been a number of large studies examining the benefits of PSA for prostate cancer screening. An American trial (PLCO trial) failed to find any benefit from using PSA levels for screening. A more detailed analysis of this trial, however, shows that it suffered from some serious methodological failings. For example, most of the men in the control group (the group that should not have undergone PSA testing) did in fact have their PSA level measured. This means that the trial was comparing two almost identical groups. Even the authors of the study have now conceded this point.

By contrast, a large European study (ERSPC trial) did find a benefit. After 13 years of follow-up, this trial found that the cancer-specific death rate was 21% lower in men with prostate cancer detected at an early stage by PSA testing. To date, however, the study has not been able to demonstrate an absolute reduction in death rate. Because prostate cancer often grows relatively slowly compared to other cancers, any such effect is only expected to become apparent after 20 years of follow-up. It is therefore not possible to definitively assess the benefit of PSA testing at the present time.

In view of these, at first sight, contradictory results and of statistical effects which are far from simple to understand, there is some controversy over the benefits of PSA testing, and this is reflected in popular reporting of this issue.
It is therefore important to talk to a specialist who knows how to interpret this test and can provide patients with expert advice.