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PSA Screening: Background

This document is not a systematic review of the evidence for or against population screening with the PSA test. It is an overview of The Prostate Cancer Charity’s position, expressed in a series of summary points for information purposes only. Further discussion of the issues can be found at NHS Cancer Screening Programmes, and a long-running debate still continues in our community. To read the personal experiences of men considering the PSA test, go to the Dipex website.

The PSA Test

• The PSA (Prostate Specific Antigen) test is a simple blood test, available from the GP.
• The PSA test helps doctors diagnose and manage prostate problems, when a man has urinary symptoms and goes to his GP for diagnosis and treatment.
• The PSA blood test can indicate the presence of a prostate problem, which may sometimes turn out to be prostate cancer. The PSA test should not, properly, be referred to as 'the test for prostate cancer,' as only in a minority of cases is it diagnostic of cancer. More often it is indicative of other, non cancerous prostate problems, for example benign prostatic hyperplasia (BPH) or prostatitis.
• If PSA levels are raised, prostate biopsy will usually be necessary to reach a diagnosis. At ‘prostate biopsy’ - a test done in hospital - a sample of tissue is taken from the gland and looked at under the microscope to see if cancer is present.
• Some people are keen on using the PSA test to screen well men for prostate cancer.

Screening men for prostate cancer

• This paper is not about the use of the PSA test when a man has symptoms which could be prostate related and he decides to visit the GP. It is about the possible widespread and systematic use of the PSA test in a Screening Programme, involving apparently well men.
• By ‘Screening Programme’ we mean a system in place where men, otherwise apparently well and symptom free, over the age of about 45, receive regular invitations to visit their GPs for the PSA blood test which might indicate the need for further tests for prostate cancer.
• The value of the PSA test in a screening role is the source of major global medical debate
• Current scientific evidence that PSA tests save men’s lives from prostate cancer is equivocal. Whilst it seems ‘obvious’ that it should, clear evidence that it does, is not yet in existence.
  
  Many men with prostate cancer believe that their lives were saved because they had a PSA test, and are keen that all men have PSA tests regularly through a Screening Programme. Other men diagnosed with prostate cancer at an advanced stage are angered that they had no early warning and support screening.
  
  Some individual medical specialists are also keen on the PSA test to screen for prostate cancer. Many other medical and scientific specialists and charitable and professional organisations have reservations about the usefulness of PSA as a potential screening test for prostate cancer in men without symptoms.’
• This is not just a UK puzzle. It is a global debate. Nowhere has a routine population Screening Programme with the PSA test, except possibly Luxemburg. The US does not, though the PSA test is used more commonly there than it is in the UK. There are extensive research studies going on in Europe and the US to test the effectiveness of PSA screening in saving lives from prostate cancer. The results are not expected for several years yet.
• It is easy to draw the conclusion that because survival apparently improves in populations of men where PSA testing is more common, clear evidence is available that PSA screening should be brought in.
  
  However, it is not that simple. Survival statistics represent the length of time men know they have the condition. If more men are diagnosed earlier, there will be an apparent ‘improvement’ in their length of survival with cancer, simply because they have been aware of their diagnosis for longer - ‘the clock starts ticking earlier.’ Survival statistics can therefore seemingly ‘improve’ when a screening test is brought in, without making any change to the time at which men start treatment and even for those men who have no treatment at all. This statistical phenomenon is called ‘lead time bias’.
  
  PSA testing is much more common in the US than the UK. A recent study of prostate cancer mortality trends in the US and UK has found that mortality rates are decreasing faster in the US. However, this study did not investigate the reasons behind the difference in rate of decline of mortality between the two countries and this cannot be understood through examining mortality trends alone. It remains unclear whether screening, differences in treatment methods or other factors are causing the differences in mortality rates. This study highlights the importance of research studies going on in Europe and the US to test the effectiveness of PSA screening in saving lives from prostate cancer.

Prostate cancer

• The PSA test will not help to identity all prostate cancers. Equally, not all cancers which it will help to identify, will need treatment.
• Most prostate cancers are slow growing and will never become life threatening. Some, of course, are aggressive and potentially life threatening.
• These aggressive prostate cancers which cause most concern will not necessarily be picked up by screening with the PSA test, as they can develop in the intervals between ‘screening.’ Some, of course, would be. Equally, not all aggressive cancers change the PSA level and would therefore avoid detection.

What happens at the moment?

• Currently, there is no Screening Programme for prostate cancer in the UK. There is unlikely to be one unless there is a shift in the evidence or better screening tests become available.
• Men who have heard of the PSA test and who have concerns about prostate cancer, but no symptoms, can talk to their GP about it and have a right to be given unbiased advice to help them decide whether or not to have a PSA test.
  
  Information about the PSA test is available under the NHS’s Prostate Cancer Risk Management Programme. If a man still wants a PSA test after the consultation and consideration of the details, he can have one free on the NHS.

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