Bristol scientists behind the largest trial ever to investigate prostate cancer screening
Press release issued: 12 March 2018
Inviting men with no symptoms to a one-off PSA* test for prostate cancer does not save lives according to results from the largest ever trial conducted by Cancer Research UK-funded scientists based at the University of Bristol.
Published on 6 March 2018 in the Journal of the American Medical Association (JAMA).
Researchers at the Universities of Bristol and Oxford found that testing asymptomatic men with PSA detects some disease that would be unlikely to cause any harm** but also misses some aggressive and lethal prostate cancers.
This highlights the flaws of a single PSA test as a way to screen for prostate cancer, and shows the need to find more accurate ways to diagnose cancers that need to be treated.
Professor Richard Martin, lead author and Cancer Research UKscientist in the Bristol Medical School: PHS at the University of Bristol, said: "Our large study has shed light on a highly debated issue. We found that offering a single PSA test to men with no symptoms of prostate cancer does not save lives after an average follow-up of ten years.
"The results highlight the multitude of issues the PSA test raises - causing unnecessary anxiety and treatment by diagnosing prostate cancer in men who would never have been affected by it and failing to detect dangerous prostate cancers. Cancer Research UK is funding work that will allow us to follow the men for at least a further five years to see whether there is any longer-term benefit on reducing prostate cancer deaths."
Dr Emma Turner, a Cancer Research UK scientist at the University of Bristol and co-author of the study, added: "Prostate cancer is the second most common cause of cancer death in men in the UK. We now need to find better ways of diagnosing aggressive prostate cancers that need to be treated early."
The CAP Trial, which spanned almost 600 GP practices in the UK and included more than 400,000 men aged 50-69, is the largest trial ever to investigate prostate cancer screening. The trial compared 189,386 men who were invited to have a one-off PSA test with 219,439 men who were not invited for screening.
After an average of ten years follow up, there were 8,054 (4.3 per cent) prostate cancers in the screened group and 7,853 (3.6 per cent) cases in the control group. Crucially, both groups had the same percentage of men dying from prostate cancer (0.29 per cent).
There is no national screening programme for prostate cancer in the UK, but men over 50 can ask their GP for a PSA test.
More than 11,000 men die of prostate cancer each year in the UK. While some prostate cancers are aggressive and lethal, others are clinically insignificant and will never lead to any harm or death if left undetected. Ideally, aggressive prostate cancers need to be identified and treated as early as possible. But finding a cancer that would never have caused men harm during their lifetime can have a serious impact on quality of life, including the worry of a cancer diagnosis, the possibility of infection following a biopsy and impotence and incontinence following treatment.
Dr Richard Roope, Cancer Research UK’s GP expert, said: "The PSA test is a blunt tool missing the subtleties of the disease and causing men harm.
"This trial illustrates that we need to develop more accurate tools if we want to save men's lives.
"Cancer Research UK's hunt for finding early stages of aggressive prostate cancer is not over. For example, we’re funding research into faulty genes which make some men more likely to develop prostate cancer and studying how these genes could help doctors to identify patients who are more at risk."
Cancer Research UK don't recommend that GPs routinely offer the PSA test to men without symptoms. If men are worried about prostate cancer they should have a full discussion with their GP.
As men over the age of 50 can still request a test, in line with the Prostate Cancer Risk Management Programme (PCRMP), we would encourage GPs to:
- Be up to date on the evidence around the PSA test.
- Encourage informed discussion with their patients about the potential outcomes of the test.
GPs should continue to use their clinical judgement when assessing men with symptoms
Cancer Research UK's advice for men is:
- If men don't have symptoms but are still worried about prostate cancer we recommend they should discuss the pros and cons of a PSA test with their GP.
- If men are experiencing symptoms it's still important for them to visit their GP as it could be a sign of a range of different conditions – including cancer.
The UK National Screening Committee does not recommend PSA screening for prostate cancer, but men over the age of 50 without symptoms can ask to be tested as per the PCRMP.
Cancer Research UK is calling for Public Health England's PCRMP to be updated to reflect the evidence from the CAP trial.
Each year there are about 47,000 cases of prostate cancer and more than 11,000 deaths in the UK and about 165,000 cases and 29,000 deaths in the US.
Videos about the CAP trial are available on YouTube.
'Effect of a low-intensity PSA-based screening intervention on prostate cancer mortality: the CAP randomized clinical trial' by Martin et al in the Journal of the American Medical Association
* Prostate specific antigen (PSA) is a protein produced by both normal and cancerous prostate cells. The PSA test is a blood test and it's normal for all men to have some PSA in their blood. Men's PSA levels can range hugely and can vary with age.
** Overdiagnosis occurs when a disease is detected but would never have gone on to cause any harm during a person's lifetime. This can happen with some cancers because they are slow-growing and unlikely to spread and cause harm, whereas others are fast-growing or aggressive and need treatment.
CAP Trial: In this randomized clinical trial, 189,386 men aged 50-69 invited for a single PSA-screen were compared with 219,439 men who were not actively invited for screening. In the control arm 219,439 men followed standard NHS management. In the screening arm, 189,386 men without symptoms between the age of 50 and 69 were invited to have a PSA test. There were about 76,000 men who took a PSA test, and about 6,900 men had a PSA level of 3.0 ng/ml or more of whom 5,830 men went on to have a prostate biopsy.
Men who were diagnosed with localised prostate cancer were then offered participation in the ProtecT trial that compared surgery, radiotherapy and active monitoring or standard NHS treatment.
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