PSA tests for prostate cancer screening
Anyone looking into the topic of PSA tests as a form of prostate cancer screening will come across conflicting information and advice. That's because neither the pros nor the cons of the test clearly outweigh each other. So the decision about whether or not to have the test is a personal decision.
This screening test is designed to detect prostate cancer before it starts causing symptoms. Early diagnosis and treatment can improve the chances of recovery and lower the risk of the cancer spreading to other parts of the body (metastasis).
But screening has clear disadvantages: It also finds small tumors that don't cause any problems. This is because in most men, prostate cancer grows so slowly that it doesn't cause any problems for the rest of their lives. Men who have prostate cancer that is detected by screening are then subjected to the burdens and side effects of the diagnosis and treatment. The diagnosis of a medical condition that would never have caused any symptoms or problems is called overdiagnosis.
PSA screening tests
The only screening test for prostate cancer that has been investigated in larger studies is the PSA test. In Germany, PSA tests are not covered by statutory health insurance. But many doctors offer the test as an individual health care service (in German: individuelle Gesundheitsleistungen, or IGeL for short), which men have to pay for themselves. The test costs between 15 and 20 euros. Because it involves a consultation and other related examinations, it often ends up costing around 50 euros in total.
The test is used to find the amount of prostate-specific antigen (PSA) in the blood. PSA is a protein that is made in the prostate gland and released into the fluid that carries sperm (called semen). PSA makes this fluid more watery so it is easier for sperm to swim in it.
To determine your PSA level, a blood sample is taken from a vein in your arm at the doctor’s practice and sent to a laboratory. It can take a few days to get the test results back. The amount of PSA in the blood is measured in nanograms per milliliter of blood (ng/mL).
What does the PSA level tell us?
Because the prostate gland has a very good blood supply, small amounts of PSA constantly pass into the bloodstream. PSA levels under 3 nanograms per milliliter (ng/mL) are considered to be normal, but there is a big gray area. High PSA levels can be a sign of prostate cancer, but may also be caused by many other conditions. The reason: If the prostate gland changes or is irritated, a little more PSA is automatically released into the bloodstream. For instance, high PSA levels may result from:
- an inflammation of the prostate gland (prostatitis),
- a benign enlarged prostate (benign prostatic hyperplasia),
- a urinary tract infection (UTI),
- pressure exerted on the prostate, for example after riding a bicycle, or after examining the prostate gland by feeling it with a finger (palpation) or doing an ultrasound scan, or
It is a good idea to let the doctor know if any of the above have occurred so that the test results can be interpreted correctly or the test can be postponed.
But normal PSA levels do not definitely rule out cancer, either. In rare cases, men have normal PSA levels despite having cancer.
But if the PSA level is very high, for example over 10 ng/mL, it is probably due to prostate cancer. PSA levels are rarely that high, though.
What problems can arise when a tissue sample is taken?
High PSA levels can be caused by many things, so abnormal test results do not mean that you have cancer. To find out whether the high PSA levels are caused by cancer or something else, tissue samples (biopsy) are usually taken from the prostate.
This involves inserting a tube about the width of a finger into the rectum (the end part of the bowel) through the anus (bottom). From there, a fine, hollow needle is pushed into the prostate through the wall of the bowel to take several tissue samples. Ultrasound is used to check that the needle is moved to the right place. Ten to twelve samples are usually taken.
Men are given antibiotics before having the procedure to prevent infections. A local anesthetic helps to prevent pain. Men often have visible blood in their urine or sperm for several days after the biopsy. About 40 out of 1,000 men have a fever for a while. About 10 out of 1,000 men end up going to the hospital to get treatment for an infection with a fever following a biopsy.
When is a biopsy recommended?
Opinions vary about which PSA levels mean that a biopsy should be recommended. The medical societies in Germany agree that a biopsy is a good idea if
- the PSA levels are higher than 4 nanograms per milliliter (ng/mL) and a second test shows the same results, or
- the PSA levels increase considerably over several measurements.
What does research on the advantages and disadvantages of PSA tests show?
A major European study looked into the advantages and disadvantages of PSA screening for men. The study involved a total of 162,000 men between the ages of 55 and 69. About half of them were offered a total of two to three PSA tests, and most of them had the tests done. The tests were typically done about four years apart. If the PSA level was over 3 ng/mL, tissue samples were taken. The other half of the men were not offered screening tests. For 13 years now, the researchers have been observing how many men have developed prostate cancer in both groups and how many have died of it.
A different PSA cut-off level was used in this study than the one typically used in Germany, though. So these results can only be used to get a general idea of what men in Germany can expect from a PSA test.
The PSA test in numbers: What results can be expected?
The data from the major European study can be used to get a rough idea of what can be expected from PSA screening.
If 1,000 men between the ages of 55 and 69 regularly have PSA screening tests over a time period of 13 years, the following results can be expected:
- About 760 men will have normal results.
- About 240 men will have a high PSA level. Most of these men will then have tissue samples taken from their prostate to check the organ for cancer cells.
- In about 140 of these men, the biopsy will not find any prostate cancer. The PSA test will have been a false alarm.
- In about 100 men with abnormal PSA levels, cancerous cells will be found. Depending on how large and aggressive the cancer is, various treatments may be considered: common ones include "active surveillance," radiotherapy or surgery.
How great are the benefits and risks of PSA screening?
- If 1,000 men participate in the PSA screening program, about 1 to 2 deaths from prostate cancer will be prevented.
- The spread of the cancer to other parts of the body (metastasis) will be prevented in about 3 out of 1,000 men.
- But the test will also detect tumors and cell changes that would never have caused any problems. This kind of "overdiagnosis" is estimated to occur in about 30 out of 1,000 men who take part in this screening program, and they may receive unnecessary treatment as a result.
The following illustration shows the pros and cons of PSA screening at a glance.
At a glance: What happens if 1,000 men have a PSA test?
As mentioned above, these numbers are estimates. On the one hand, different PSA cut-off levels are recommended in Germany. Also, the men in the study were observed for only 13 years on average afterwards. A longer observation period could lead to different results.
Making a decision
Whether a man finds that the possible advantages of PSA screening tests outweigh the possible drawbacks will depend on his personal situation and preferences. You can take your time when deciding whether or not to have the test. There are good reasons both for and against having PSA screening tests, so no man should feel pressured into having them.
Chou R, Croswell JM, Dana T, Bougatsos C, Blazina I, Fu R et al. Screening for prostate cancer: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2011; 155(11): 762-771.
Deutsche Gesellschaft für Urologie (DGU). Interdisziplinäre Leitlinie der Qualität S3 zur Früherkennung, Diagnose und Therapie der verschiedenen Stadien des Prostatakarzinoms. AWMF-Register-Nr.: 043/022OL. December 2016. (Leitlinienprogramm Onkologie).
Fenton JJ, Weyrich MS, Durbin S, Liu Y, Bang H, Melnikow J. Prostate-Specific Antigen–Based Screening for Prostate Cancer: A Systematic Evidence Review for the U.S. Preventive Services Task Force. April 2017. (AHRQ Evidence Syntheses; Band 154).
Loeb S, Vellekoop A, Ahmed HU, Catto J, Emberton M, Nam R et al. Systematic review of complications of prostate biopsy. Eur Urol 2013; 64(6): 876-892.
Schröder FH, Hugosson J, Roobol MJ, Tammela TL, Zappa M, Nelen V et al. Screening and prostate cancer mortality: results of the European Randomised Study of Screening for Prostate Cancer (ERSPC) at 13 years of follow-up. Lancet 2014; 384(9959): 2027-2035.
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