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Using the much-maligned PSA test to systematically screen men for prostate cancer can reduce their risk of dying from the common cancer by 20 per cent or more, according to new research.

The study, to be published Thursday in the New England Journal of Medicine, confirms that using the prostate specific antigen test results in more frequent and earlier diagnosis. It also shows for the first time that, if the test is done routinely over a long period of time, mortality rates fall much more sharply than if testing is done higgledy piggedly, as is now the case.

“A lot of men are getting the PSA test now, but if you do it in an organized fashion, a lot more will benefit,” said Bob Shiell, president of the Canadian Prostate Cancer Network.

His group recommends that all men over the age of 40 get a PSA test as part of regular check-ups, and that they track any changes that might point to the presence of cancerous tumours.

The new study, however, showed a benefit only to men aged 55 to 69.

The research team, led by Fritz Schroder of Erasmus Medical Centre in Rotterdam, The Netherlands, followed more than 162,000 men for a decade on average. Over a decade, 8.2 per cent who took the PSA test annually were found to have prostate cancer, compared to 4.8 per cent of men in the control group.

There were 261 deaths among those who were routinely screened, compared to 363 deaths in men who received routine care. That is a 20-per-cent relative reduction, and researchers predicted mortality would fall even further over time as prostate cancer is slow-growing.

However, a second study, also published in the New England Journal of Medicine, produced far more mitigated results. That research, led by Dr. Christine Berg of the U.S. National Cancer Institute in Bethesda, Md., found no difference in mortality between men who were screened routinely with the PSA test and those who were not in a screening program.

There were almost 77,000 participants aged 55 to 74 who were followed for 10 years. In that study, rates of cancer were higher in the screening group (7.3 per cent) than in the routine care group (6 per cent.) However, there were 92 prostate cancer deaths in the screening group, compared to 82 in the control group, a difference that was not statistically significant.

Both studies stressed that men need to be aware of potential risks of PSA testing, in particular that there are false positives (meaning men think they have cancer when they do not), and testing can lead to unnecessary treatment. Because of these risks, the value of PSA screening has been fiercely debated and the mortality research was supposed to help resolve the debate.

PSA is a protein produced by the cells of the prostate gland, a walnut-sized organ located below the bladder and in front of the rectum. High PSA levels can suggest the presence of prostate cancer. The numbers can also be elevated due to prostate infection or recent ejaculation, and PSA levels rise with age.

Heather Chappell, senior manager of cancer control policy at the Canadian Cancer Society, said while the new research adds important elements to knowledge about benefits and risks of PSA testing, the group will not change its approach. The Cancer Society recommends that men aged 50 and older discuss the benefits and risks of PSA testing with their physician.

Prostate cancer is the most common cancer in Canadian men. In 2008, an estimated 24,700 men were diagnosed with prostate cancer and 4,300 died of the disease, according to the Canadian Cancer Society.