March is widely recognised as prostate cancer awareness month - a disease that affects nearly 40,000 men in the UK every year, and many hundreds of thousands more worldwide. But while we have screening programmes over here for breast, cervical and bowel cancer, we don't have a national screening programme for prostate cancer, even though there is a blood test - the PSA test - which measures the levels of PSA, a protein produced by the prostate gland that can be raised in men with prostate cancer.
The reason for this is because doctors simply don't know how reliable the PSA test is. The problem is that PSA levels can be raised by a number of non-cancerous conditions, so it's not very specific. And there's also a small but significant proportion of men with prostate cancer who don't have raised PSA levels.
And finally, even if a man does have a raised PSA level, and does have prostate cancer, it's hard to know whether it's an aggressive cancer that needs urgent treatment - and along with that comes the risk of serious side effects - or a slow-growing cancer that can be safely monitored over time. But if the test does pick up aggressive cancer at an early stage, it can save a man's life.
Because of this confusion, many research teams around the world have been carrying out large studies to find out whether the benefits of PSA testing across large populations outweigh the risks. But, frustratingly, new results following up a big study of prostate screening don't provide any firm answers.
These are results from the European Randomised Study of Screening for Prostate Cancer - known as the ERSPC - which was set up in 1991 to try and figure out the effectiveness of PSA testing, looking at men in the Netherlands and Belgium, as well as Sweden, Finland, Italy, Spain and Switzerland.
These new results - following up more than 180,000 men after 11 years - have just been published in the New England Journal of Medicine. In the study, the men were divided into two groups - one were given PSA testing roughly once every four years, while the other group were left unscreened - but, of course, were free to go to the doctor if they noticed any unusual symptoms.
The researchers discovered that the death rate from prostate cancer was just over 20 per cent lower in the men who were PSA tested than untested men. But after further calculations, the scientists showed that in order to prevent one death from prostate cancer during the 11-year period, more than 1,055 men would need to be invited for screening, with nearly 40 cancers detected.
This chimes with results from the same study published two years ago. Meanwhile, a similar study in the US has also found that PSA testing has little impact on saving lives from prostate cancer, but may be leading to men being more likely to have treatment causing side effects such as impotence and incontinence for a cancer that may not be aggressive.
At the moment, men in the UK are advised to discuss PSA testing with their GP, who can outline the risks and benefits. But this study - and the others like it around the world - only serve to highlight the problems with the PSA test, and the urgent need to develop better tools for detecting aggressive prostate cancers at an early stage that will save lives, while avoiding men having to go through unnecessary treatment for tumours that are unlikely to be dangerous.
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