Prostate cancer screening trial raises concerns about 'false positive' results
A large European trial has cast doubt over the viability of prostate cancer screening, concluding that one in eight men receive a positive test result when they do not have the disease.
Researchers studied the outcome of prostate specific antigen (PSA) testing, which shows the amount of a protein produced by prostate cells in the blood.
High PSA levels may signal prostate cancer, but the protein may also be raised by infection, a non-cancerous enlarged prostate or even recent exercise.
PSA testing is not routinely offered in the UK, although men can discuss the risks and benefits with their doctor if they are concerned that they may have prostate cancer.
In March 2009, scientists announced early data from the European Randomised Study of Screening for Prostate Cancer (ERSPC), which suggested the test may cut deaths from the disease by 20 per cent.
But the Finnish part of the trial - which is being conducted in seven countries - has now reported that for every eight men screened on a four-yearly basis, one received a false positive result.
This was true even if the threshold for PSA was set fairly high.
The findings, which are published in the British Journal of Cancer, suggest that many men would undergo invasive tests such as biopsies unnecessarily, as well as potentially receiving treatment that they did not need.
Furthermore, the study found that men who received a false positive result were twice as likely to refuse screening in the future.
Lead researcher Dr Tuomas Kilpelainen, from the University of Tampere in Finland, told the BBC: "I don't think routine screening should be advised until more is known on the adverse effects and costs of screening.
"If a man has urinary tract symptoms and is concerned he could have prostate cancer, the most important thing is to consult a GP or a urologist."
Professor Julietta Patnick, director of the NHS Cancer Screening Programmes, observed that according to the study findings, 48 men would have to be treated in order to save one life.
"False positives are an issue for any screening programme, and this Finnish paper is very helpful at gaining an understanding of how they might figure in the context of prostate screening," she added.
Professor Peter Johnson, Cancer Research UK's chief clinician, commented: "This paper shows that there are two sides to using the PSA test to screen men for prostate cancer. Although for some men detecting prostate cancer early through screening can be life saving, on the other hand the test will be abnormal for around one man in eight without cancer being detectable at that time.
"Further tests and biopsies are usually needed to rule out cancer for these men. For this reason it is important that men in their 50s and 60s can talk to their doctor about the pros and cons of having a PSA test and only have the test if they feel it is right for them."