Screening for prostate cancer does not save lives, and may do more harm than good, a major study has concluded.
The largest ever trial of PSA (prostate specific antigen) tests - which all men over 50 can obtain on request from their GP - found that death rates were identical among men, whether or not they underwent screening.
Inviting symptomless men for the one-off blood test detects some tumours unlikely to be harmful - while still missing others that were fatal, researchers warned.
The study, funded by Cancer Research UK, follows a long debate about whether the NHS should introduce routine screening, using the tests.
Lead author Professor Richard Martin, a Cancer Research UK scientist at the University of Bristol, said: "Our large study has shed light on a highly debated issue.
prostate cancer cases
"We found offering a single PSA test to men with no symptoms of prostate cancer does not save lives after an average follow up of 10 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."
Prostate cancer is different to other forms of the disease in that while some are aggressive, most do not cause any symptoms. Men can survive without treatment.
But it is not possible to distinguish between the two types using the current blood test for prostate-specific antigen (PSA), a protein produced by the gland where higher levels make cancer more likely.
The facts | Prostate cancer
The new 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.
It 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 10 years follow up, there were 8,054 (4.3 per cent) prostate cancers in the screened group and 7,853 (3.6 cent) cases in the control group.
But crucially, both groups had the same percentage of men dying from prostate cancer - at 0.29 per cent.
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Experts said the findings, published in the Journal of the American Medical Association, showed an urgent need to find a new way to diagnose - prostate cancer, which is the second biggest cause of cancer deaths in men.
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.
Over-diagnosis leads to unpleasant or damaging treatment for cancerous cells so slow growing they would not have caused any problems if left undetected.
Prostate cancer therapy, such as surgery, can leave men with significant complications - including impotence and incontinence.
Each year there are about 47,000 cases of prostate cancer and more than 11,000 deaths in the UK.
The UK National Screening Committee does not recommend PSA screening for prostate cancer.
But men over the age of 50 without symptoms can ask their GP for a PSA test.
Co author Dr Emma Turner, a Cancer Research UK scientist also at the University of Bristol, said: "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."
Prostate and Breast cancer deaths in UK
GP expert Dr Richard Roope, of Cancer Research UK which funded the study, 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.
"We do not recommend that the PSA test should be routinely offered to men without symptoms. However, if a man is particularly worried about his risk of prostate cancer, he should have a full discussion about his risk with his GP."
Previous UK research has found to prevent one death from prostate cancer, 1,410 men would need to be screened and 48 treated.