What does PSA mean? What is the significance of the PSA test in the early detection of prostate cancer? What are the advantages and risks? Experts from the West German Prostate Center (WPZ) at the KLINIK am RING in Cologne answer the most important questions about PSA.
PSA - what is it?
PSAis an abbreviation for "prostate specific antigen". This is a protein that is formed exclusively by prostate cells and serves to liquefy the sperm. Since the prostate is very well supplied with blood, small amounts of PSA are constantly entering the blood. To determine the PSA value, a blood sample is taken and the PSA concentration is determined in the laboratory. The PSA value is expressed in nanograms per milliliter of blood (ng/ml).
What does the PSA value tell you?
The prostate-specific antigen is produced by every prostate cell. A PSA value in the normal range therefore usually also indicates normal prostate activity. If the prostate enlarges, the prostate cells produce more PSA, which can be reflected in an "elevated" PSA value. Prostate Specific Antigen is a tissue marker and NOT a tumor marker. Therefore, the test result only ever predicts the likelihood that prostate cancer is present. Thus, there are numerous reasons why blood PSA may be elevated in the short term. Conversely, a normally high PSA level does not automatically mean that there is no prostate cancer.
For what reasons can the PSA value be elevated?
By no means every patient whose blood exceeds the limit value of 4 ng/ml suffers from prostate cancer. This is because urinary tract or prostate infections, benign changes, as well as pressure on the prostate, e.g. from a digital-rectal examination or from sports activities such as cycling or horseback riding, but also sexual intercourse and ejaculation can cause the PSA in the blood to rise for a short time. It is therefore all the more important not to panic in the event of one-time elevated PSA values, but to repeat the test several times and additionally use other diagnostic procedures.
What should be taken care of before taking blood for the PSA test?
Since the prostate is sensitive to pressure, mechanical irritation can boost PSA production and falsify the result of the PSA test. Urologists therefore recommend avoiding cycling and sexual intercourse two to three days before taking blood for PSA measurement. Palpation of the prostate can also increase the PSA level in the short term and should always be performed after the blood sample for PSA determination.
When and how often should the PSA test be performed?
According tothe current guidelines of the German Society of Urology (DGU), the test is recommended from the age of 45 years (in case of familial disposition from 40 years). How often the test should be repeated depends on the test result: If a PSA value of less than 1ng/ml was measured, a further check is only necessary after 4 years. If the value is above 2 ng/ml, an annual control should take place. In case of lower values, the interval of PSA determination can be extended after evaluation by the urologist.
At what point is the PSA test suspicious?
In general, PSA values between 0 ng/ml and 4 ng/ml are considered "normal". In contrast, values between 2ng/ml and 4ng/ml are considered to be in need of control. However, in order to be able to assess the test result, not only the absolute level of the PSA value but above all changes over time as well as the age of the patient play an essential role.
Age & Normal Value
PSA standard values depending on age (source: DGU)
Is the PSA test alone sufficient to make a tentative diagnosis?
However, the one-time measurement of the PSA value has only limited significance and is not sufficient on its own to make a diagnosis. An elevated PSA value can also have other reasons. It is therefore important to repeat the test promptly and, if necessary, to use other diagnostic procedures in addition to ultrasound and palpation for further clarification. It is essential to always make a professional, well-founded assessment of a man's overall findings and not to evaluate the PSA test result in isolation. If the overall results do indeed indicate prostate cancer, tissue samples are taken from the prostate and examined in the laboratory for cancer cells (prostate biopsy).
What is the significance of the PSA test in the early detection of prostate cancer?
The PSA test is currently the only screening test that can detect prostate cancer at a very early, easily curable stage. For example, the introduction of the PSA test in the 1980s has resulted in prostate tumors being detected on average about five years earlier. This is the crucial time when curable disease stages can become incurable disease. The European Screening Study (ERSPC) has shown that the risk of dying from prostate cancer can be halved by PSA-based screening.
Why is the PSA test controversial?
PSA opponents often argue that most men die with their prostate cancer, not from it. In fact, the PSA test can also detect "non-relevant" carcinomas that might not have led to the patient's death. Left unnoticed is the fact that, according to the Robert Koch Institute, there are still 11,000 to 12,000 deaths from prostate cancer each year - patients whose diagnosis is "incurable" because in many cases it was detected too late. Withholding the PSA test from patients deprives men with an aggressively growing tumor, which without adequate therapy would lead to death, of the possibility of a cure.
Are palpation and ultrasound insufficient for early detection of prostate cancer?
Early detection of prostate cancer by digital rectal examination (DRU) alone is insufficient and often a "late detection". During DRU, the urologist palpates the prostate from the rectum to detect possible indurations that may indicate a tumor. However, palpation can only detect superficial tumors that have reached a certain size. The disease may then already be in an advanced stage and is only curable to a limited extent. Studies show that out of 12 patients with prostate cancer, 11 cases are detected by measuring the PSA level and only 1 case by digital-rectal examination.
What are the risks of the PSA test?
Although the guideline for the early detection, diagnosis and treatment of prostate cancer gives clear recommendations on when and under what circumstances the test should be used, it still happens that PSA values are misinterpreted and hasty "action" is taken. For example, a biopsy is often ordered on the basis of briefly elevated PSA values, instead of initially observing the progression of the values. Or patients with a low-risk stage are treated unnecessarily with invasive therapy such as surgical removal of the prostate (prostatectomy). Overtreatment of prostate cancer - i.e. unnecessary treatments with possible side effects - is a major problem in Germany. However, it is not the PSA test that is to blame for this, but the way the results are handled.
What role does the measurement of the PSA value play after the end of therapy?
When treatment is completed, follow-up care begins. Here, too, the PSA test plays an essential role. Regular checks of the PSA value are intended to ensure that a relapse (recurrence) after surgery or radiation therapy is detected in good time. Tumor cells that have settled in the body as metastases outside the prostate also produce PSA. Thus, PSA is measured every three months within the first two years, every six months in the third and fourth years, and every 12 months after five years. This applies to radical prostatectomy as well as external beam radiation and brachytherapy.
How does the PSA value behave if the prostate cancer recurs?
If the prostate was surgically removed with the tumor (radical prostatectomy), the PSA level should drop below the detection limit (below 0.2 ng/ml) within four to six weeks. If the PSA level rises, it could be that the tumor is growing again. A relapse (recurrence) after radical prostatectomy is when the PSA level rises above a value of 0.2 ng/ml in two consecutive measurements. In technical terminology, such a case is referred to as "biochemical recurrence" or "PSA recurrence". If, on the other hand, brachytherapy or external beam radiation has been performed, the PSA level will slowly decrease over months. The lowest value ("nadir") varies from individual to individual.
Does a PSA rise after brachytherapy automatically mean a recurrence?
In more than one third of all patients with prostate carcinoma treated with brachytherapy, a primary drop in PSA is followed by a renewed increase, which in turn falls spontaneously after some time. Such a temporary PSA increase usually occurs 1 to 1 ½ years after brachytherapy and decreases again after an average of 18 to 20 months. The reason for such a PSA bounce is usually radiation-induced inflammation of the remaining prostate tissue (prostatitis), which, however, does not require treatment. A short-term increase in PSA after brachytherapy therefore does NOT indicate renewed tumor growth in the prostate (local recurrence) in most cases.