Science

Expert controversy over cancer screening test

The dispute has been smoldering for decades. And it is currently being conducted more intensively than ever: is the PSA test suitable for the general early detection of prostate cancer in men? Opinions differ widely.

“The PSA value is the essential marker for prostate tumors,” says Jens Rassweiler, head of urology at the SLK clinics in Heilbronn and president of the German Society for Urology (DGU). “It is highly informative, which is why we want it as a health insurance benefit.” The head of the Institute for Quality and Efficiency in Health Care (IQWiG), Jürgen Windeler, contradicts this: “The test leads to many overdiagnoses and overtreatments. Urologists trivialize this. »

At the beginning of January, after evaluating the study situation, the institute published a preliminary report on the advantages and disadvantages of early PSA detection. The benefit of such a screening does not outweigh the associated risks, it says: “Screening does benefit some men by saving or delaying exposure to metastatic cancer.

Unnecessary therapy, then impotence

In return, however, significantly more men have to reckon with permanent incontinence and permanent impotence due to overdiagnosis and over-therapy, and in relative terms young age. »

Prostate cancer is the most common type of tumor in men. In the year 2016 the Robert Koch Institute (RKI) registered just under 59 000 New diseases, round 14 400 patients died of cancer in that year. The mean age of the initial diagnosis is 72 years. A special feature is that many prostate tumors grow so slowly that they do no harm.

Despite the frequency of the type of cancer, there is currently no general program for early detection – in contrast to mammography screening for breast cancer. From the age of 45 years, the health insurance companies pay for a tactile examination of the prostate from the intestine. However, their benefit is minimal: the doctor can only feel thickening or hardening of the prostate gland on the side of the intestine.

The PSA test measures the level of the prostate-specific antigen (PSA) in the blood. This enzyme is made by the prostate to liquefy the semen. Tumors can cause PSA to get into the blood. The higher the value, the greater the risk that a tumor will grow in the prostate – considered to be noticeable in 50 – year-olds a PSA Concentration from 3 nanograms per milliliter.

Marker yes, reliable no

It is undisputed that PSA is the best marker for prostate tumors. But is it good enough for general and funded prostate cancer screening? Urologists and many general practitioners recommend the test to men, which costs about 20 euros.

The problem: Because other factors such as sex, cycling and, in particular, inflammation can increase concentration, a high PSA value is not a reliable indicator of a tumor. Conversely, a low value does not guarantee freedom from tumors. A biopsy, in which a tissue sample is punched out of the organ and analyzed, must provide certainty in the event of a suspicion.

The biopsy gives the all-clear in around two thirds of the suspected cases. Then the patient has at least an information gain, says DGU President Rassweiler. The risk of serious problems such as inflammation from a biopsy is 0.7 percent, says Rassweiler with reference to a US study.

The situation is different for overdiagnoses and overtreatments – in other words, if tumors are found and treated that would not be a problem for a man in life. Even the diagnosis of a potentially fatal illness is harmful to those affected, according to the IQWiG. Above all, the therapies were associated with considerable risks.

Benefit: yes. Damage: too. What predominates?

In order to clarify the relationship, the institute evaluated eleven studies with more than 400 000 participants. They either had PSA screening or not, and were then followed for up to 20 years. Results: According to the IQWiG, the examination saved 3 of 1000 patients from metastatic prostate cancer within twelve years. Within 16 years, the screening saved 3 of 1000 men from dying from prostate cancer. However, this did not have an impact on overall mortality – according to IQWiG, it may also be because the rescued participants died of another disease at a comparable time.

Conversely, about 35 to 60 from 1000 men receive an unnecessary diagnosis of prostate cancer, which can lead to serious and long-lasting complications, according to the IQWiG. What this means is described by the head of urology at the University Hospital Düsseldorf, Peter Albers: The incontinence risk after an operation is strongly age-dependent. It is at 50 year olds at about 1 percent, at 70 – year-olds, however, at about 10) percent. “Impotence is a much more serious factor,” he emphasizes. «At 50 – year-olds also had nerve-preserving surgery 20 to 30 percent of patients experience erectile dysfunction permanently. You should know that beforehand. ”

There are overdiagnoses and overtreatments in other types of cancer, says IQWiG boss Windeler. But with prostate cancer they are round 10 times more often than with breast cancer. “That is another dimension,” said the epidemiologist. “The relationship between overdiagnosis and overtreatment to prevented deaths is the main weakness of PSA screening.”

Opinion

Urologist representative Rassweiler criticized, other studies would come to a more favorable ratio for PSA screening than presented in the IQWiG preliminary report. In any case, urologists were now more selective than before: “We take a PSA value as the base value,” he explains. “If this is noticeable, a second measurement follows a few months later.” A biopsy can only be initiated if it confirms the previous result. “We preselect by the course of the PSA value.”

If the suspicion is confirmed, the patient can freely decide whether he prefers immediate treatment or wants to wait until the tumor has developed, says Rassweiler. However, he advises therapy. “There is always a certain risk.”

Precisely because of this imponderability, Windeler sees men in the dilemma after a positive finding: “This is an extremely difficult decision situation. For many patients it is difficult to bear to live with a tumor diagnosis and to do nothing. »

But how can the problem be solved? Prostate tumor markers better than PSA are not in sight. “Despite its limitations, PSA is likely to remain the only biomarker for prostate cancer screening for the foreseeable future,” wrote University College Dublin's Michael Duffy recently in the journal Clinical Chemistry and Laboratory Medicine.

In Germany an investigation is trying to clarify whether the PSA value could be suitable for screening. The 2014 started probase study is testing a so-called risk-adapted screening in four centers 47 000 Participants: With them, a PSA base value is initially determined – either with 45 or only at 50 years.

Additional diagnosis via MRI

This value then decides how often the participants up to the age of 60 years to be tested. If it is below 1.5 ng / ml, further PSA tests are only carried out every five years. This probably affects more than 90 percent of the participants, says study leader Albers, who heads the “Personalized early detection of prostate cancer” area at the German Cancer Research Center (DKFZ). With a value of 1.5 to 2, 99 tests are scheduled every two years, with a value from 3 ng / ml further tests follow. “This would have different risk groups with different screening frequency,” says Albers.

According to the first results, the rate of carcinomas at the age of 45 years extremely low at 0.2 percent – according to Albers, it is 1.0 to 1.2 percent for breast cancer. This could possibly indicate that the beginning of a screening from 50 would be sufficient. The study examines the frequency of metastatic prostate cancer at the age of 60 in both groups. The final results are expected in about ten years.

Ultimately, every man has to decide for himself whether he wants to have a PSA test or not. If you are considering the test, Albers recommends that you obtain very detailed information and, if you have any questions about a urological specialist, it is best to contact one of the 100 certified prostate cancer centers nationwide .

In addition, the inclusion of modern MRI devices could reduce the proportion of overdiagnoses: “We recommend that every patient with a high PSA value should have a high-quality MRI before a biopsy.” There is an advantage among other things, that they do not indicate low-risk carcinomas. “This way we avoid unnecessary diagnoses of low-risk carcinomas and detect the aggressive carcinomas.” The MRI costs from 400 to 500 However, the patient usually has to pay euros himself.

Even if a biopsy confirms a suspected cancer, a tumor does not always have to be removed. “We promote active monitoring of tumors with low risk” – about once a year with an MRI including a PSA test. On the basis of the pathological finding, one can estimate the aggressiveness of a tumor with a 90 – percentage probability, he says. This may delay or even avoid surgery. Nevertheless, he admits: “If the results are positive, you can quickly get into a machine.” ( Walter Willems, dpa )

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