The study, which has not yet been published, compared surgically removing the prostate gland with 'watchful waiting' and found there was little difference between the two.
Experts are believed to be 'shaken' by the news because thousands of men could have gone through painful and unnecessary surgery.
A new study suggests that surgery makes little or no difference to prostate cancer sufferers
The Prostate Intervention Versus Observation Trust (PIVOT), led by Timothy Wilt, started in 1993 and analysed 731 patients over 12 years.
It found that those who had an operation to treat the cancer had less than three per cent chance of survival compared with those who had no treatment.
The results were presented at a meeting of the European Association of Urology in Paris in February and were met with a stunned silence.