Prostate cancer screening results could be misleading, Finnish trials confirm.
One in eight men screened could test positive when they do not have the disease, it was found.
A positive result can mean undergoing invasive tests such as biopsy as well as potentially unnecessary treatment.
Early data from the European Randomised Study of Screening for Prostate Cancer, which is being conducted in seven countries, showed in March 2009 that deaths could be cut by 20%.
But other recent evidence has cast doubt on the long-term benefits of screening, suggesting some men may end up being "over-treated" for slow-growing disease that would never cause a problem in their lifetime.
Those men who tested positive in the Finnish leg but later found not to have cancer might not go for screening again, thus putting their own lives in danger, the British Journal of Cancer reported
Study leader, Dr Tuomas Kilpelainen, said: "I don't think routine screening should be advised until more is known on the adverse effects and costs of screening.
"If a man has urinary tract symptoms and is concerned he could have prostate cancer, the most important thing is to consult a GP or a urologist."
Results from both the European trial and a large study being carried out in the US are due this year, Cancer Research UK said.
Professor Peter Johnson, Cancer Research UK's chief clinician, said the paper showed there were "two sides" to using PSA for prostate cancer screening.
"Although for some men detecting prostate cancer early through screening can be life-saving, on the other hand the test will be abnormal for around one man in eight without cancer being detectable at that time.
"For this reason, it is important that men in their 50s and 60s can to talk to their doctor about the pros and cons of having a PSA test and only have the test if they feel it is right for them."