PSA tests for prostate cancer screening

Photo of a man sitting on the grass (PantherMedia / Wavebreakmedia ltd) The PSA test for prostate cancer screening has pros and cons: It can prevent 3 out of 1,000 men from dying of prostate cancer. But it also leads to an unnecessary prostate cancer diagnosis in up to 60 out of 1,000 men – who often have unnecessary cancer treatment as a result. The decision about whether or not to have the test is a personal decision.

The aim of doing PSA tests is to discover prostate cancer before it causes any 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 this screening also has clear disadvantages: It finds many small tumors that aren't a medical concern. 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 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 a doctor has examined the prostate gland by feeling it with a finger (palpation) or doing an ultrasound scan, or
  • ejaculation.

It is a good idea to let the doctor know if any of the above have recently 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 prostate 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.

When is a biopsy done?

High PSA levels can be caused by many things, so abnormal test results don't necessarily mean you have cancer. To find out whether the high PSA levels are caused by cancer or something else, a tissue sample (biopsy) is usually taken from the prostate.

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 problems can arise when a tissue sample is taken?

The biopsy 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, fine, hollow needles are pushed into the prostate through the wall of the bowel to take several tissue samples. Ultrasound is used to check that the needles are moved to the right place. Ten to twelve samples are usually taken.

The men are given antibiotics before the procedure in order to prevent infections. A local anesthetic helps against the pain.

Men often have visible blood in their urine or sperm for several days after the biopsy. They may also have temporary problems when urinating or temporary erection problems.

About 2% of all men who have this kind of biopsy have complications such as an infection. Some men have to go to hospital as a result.

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 had two to three PSA tests on average. 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 16 years now, the researchers have been observing how many men have developed prostate cancer in both groups and how many have died of it.

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.

So these results can only be used to get a general idea of what men in Germany can expect from a PSA test. One reason for this is because a different PSA cut-off level was used in this study than the one typically used in Germany. If 1,000 men between the ages of 55 and 69 regularly have PSA screening tests over a time period of 16 years, the following results can be expected:

  • About 620 men will have normal results.
  • About 380 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 250 of these men, the biopsy will not find any prostate cancer. The PSA test will have been a false alarm.
  • In about 130 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.
  • Up to 60 of these men would never have noticed that they have prostate cancer – and it would never have caused any problems.

How great are the benefits and risks of PSA screening?

  • Benefits: For every 1,000 men who have a PSA test, about 3 of them will be prevented from getting metastatic tumors and dying of prostate cancer.
  • Harms: But the test will also detect tumors and cell changes that would never have caused any problems. This kind of "overdiagnosis" occurs in about 60 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.

Illustration: At a glance: What happens when 1,000 men take part in the screening program over a time period of 16 years?At a glance: What happens when 1,000 men take part in the screening program over a time period of 16 years?

As mentioned above, these numbers are estimates. That's partly because different PSA cut-off levels are recommended in Germany. Also, the men in the study were observed for 16 years on average afterwards. A longer observation period could lead to different results.

Making a decision

PSA tests can prevent some men from dying of prostate cancer. In other men, this screening test causes harm overall because it can lead to overdiagnosis – and unnecessary cancer treatment. So it's worth carefully considering the pros and cons of this screening test before deciding whether or not to have it. The advantages and disadvantages are summarized in the following table.

Reasons to have the PSA test Reasons not to have the PSA test
  • Reduces the risk of dying of prostate cancer
  • Reduces the risk of the cancer progressing and spreading (metastasis)
  • Often leads to overdiagnosis and unnecessary cancer treatments
  • Overdiagnosis can result in incontinence and erection problems
  • Screening can't prevent prostate cancer from developing

When making a decision, it's important to remember that some of the potential disadvantages of unnecessary cancer treatment occur straight after having the treatment. These include incontinence and erection problems. The possible advantage of screening – preventing death due to prostate cancer – usually only occurs after 10 years or more.

Every man should decide for himself whether or not he would like to have a PSA test to screen for prostate cancer. He can take his time to decide. Nobody should feel pressured into having this screening test.