Prostate cancer is a major killer
Routine screening for prostate cancer has come under further scrutiny after two studies concluded it may do more harm than good.
European researchers found the current prostate specific antigen (PSA) test cannot reliably rule out a future diagnosis of prostate cancer.
Another article, also in the British Medical Journal, found the long-term benefits of screening were unclear.
Although there is no formal screening in the UK, PSA testing is on the rise.
It is not offered as standard but men can ask their GP for the test.
In March, ministers asked the UK National Screening Committee to review the existing advice on screening after a large European study reported it could cut deaths by 20%.
A final decision will not be made until next summer.
In the latest Swedish study, the researchers looked at the results of PSA tests in 540 men done several years before they were diagnosed with prostate cancer and compared them with results from 1,000 healthy men.
They could not reliably find a cut-off point at which a PSA test predicted future prostate cancer.
Only very low PSA concentrations - less than 1ng/ml - virtually ruled out a later diagnosis, they found.
NHS recommendations advise referral at 3ng/ml in men aged 50-59 and up to 5ng/ml in older men.
Better ways of detecting prostate cancer are needed before screening can be recommended, they concluded.
In the second paper - an analysis of the current evidence on screening - US researchers said there was still too little known about screening.
They said over-diagnosis due to screening could be as high as 50% and said it was not clear how much overtreatment was happening because of PSA testing.
Unnecessary treatment carries a risk of side-effects such as impotence and incontinence.
Men need to be advised that the test cannot tell whether they have a life-threatening cancer and could take them through a "thicket of tests and treatments that they might have better avoided", the report added.
Prostate cancer is now the second most common cause of cancer deaths in men in the UK.
In July, GPs were issued with updated advice on using PSA tests.
Dr James Kingsland, a GP in Wallasey, Merseyside, and member of the government's scientific advisory group on prostate cancer risk management, said the latest research reinforces the current decision not to offer screening more widely in the UK.
"It is using a test for something which it was never designed for, which is always dangerous.
"These are helpful studies but some people will be disappointed."
He said better tests were being developed and in the meantime GPs should explain the risks and limitations of the PSA test to healthy men who ask for it.
A spokeswoman for the National Screening Committee said they had commissioned researchers at Sheffield University to produce various models of what a screening programme in the UK would actually look like, the results of which will inform the decision on whether to introduce screening.