Prostate cancer is the most common cancer in men

The PSA test is based on the theory that people with prostate cancer produce high levels of a protein called prostate-specific antigen.

But the new study, led by Boston's Massachusetts General Hospital, suggests the rate of increase of PSA may be the most important factor.

The research is published in the New England Journal of Medicine.

The researchers, who studied 1,095 men, found that when PSA levels rose by at least two points during the year before they underwent surgery, about one in four patients died from the disease within seven years.

This was ten times the average death rate among men with the disease.

However, if the PSA level had been increasing slowly before surgery, there was very little chance that the patient would die from a prostate tumour.

Lead researcher Dr Anthony D'Amico said: "This study provides, for the first time, solid evidence that PSA testing over a period of time is a reliable indicator of possible risk of death from prostate cancer."

He is recommending annual tests for men aged 35-40 to establish their baseline PSA level.

Doubts

The use of the PSA test to diagnose prostate cancer is controversial because raised levels of the protein do not always indicate the presence of cancer.

Production of the protein can also be triggered by much less serious infections.

However, if a man's PSA looks high, doctors will often recommend removal of a tissue sample for further tests.

Dr Chris Hiley, of the Prostate Cancer Charity, welcomed the research.

She said: "This research means that doctors will be able to tell men with prostate cancer more about what to expect in the future after their prostate glands have been removed.

"The researchers clearly believe that the case for annual PSA testing to screen for prostate cancer is proven.

"However, there are divergent medical views in the US and beyond on the value of PSA screening of all men.

"So screening younger men, aged 35-40, will not necessarily be a view that is widely shared.

"The Prostate Cancer Charity believes that all men need to know that PSA testing is available from their GP, but that it is not yet clear if lives are saved by the test.

"Men need to be fully informed of the risks and benefits of this type of testing. We need more research."