Studies show small benefit or none at all to prostate-cancer screening

Two large international studies added fuel to the controversy Wednesday over whether prostate cancer screening saves lives of middle aged men.

The U.S. and European studies tracked the health of over 250,000 men. The U.S. study found no benefit from cancer screening, and the other study detected only a modest 20 per cent reduction in deaths.

The screening test in question is a blood test that measures levels of prostate-specific antigen, or PSA. When levels are high, a biopsy is needed to confirm a tumour, which could be so slow-growing that it doesn't pose a threat.

"The hope was … that there'd be a clear answer," said Dr. Michael Barry of Massachusetts General Hospital, who wrote an editorial accompanying the studies in Wednesday's online issue of the New England Journal of Medicine.

'My interpretation of the two studies together is that PSA screening likely does save some lives but does significant more harm.' —  Dr. Otis Brawley

"Either that there was so little or no benefit that it clearly wasn't worth the risks. Or that the benefit was so large, that it was. What we're left with is something in between — that the benefit is fairly small … and the risks are pretty big."

The main risk is the detection and treatment of clinically insignificant cancers that are not fatal, which can lead to needless medical procedures.

So far, experts say the advice in most guidelines stands: talk to your doctor about the pros and cons of having the tests before deciding whether it is the right choice for you.

Risk of overdiagnosis

Prostate cancer is the most prevalent cancer in Canadian men. In 2008, an estimated 24,700 men will be diagnosed with prostate cancer and 4,300 will die of it, according to the Canadian Cancer Society.

Canadian Dr. Anthony Miller, a professor in public health at the University of Toronto, worked on the U.S. study that followed 76,693 men, age 55 to 74, over 10 years. Half of the participants got six annual PSA tests and four digital rectal exams or regular care from their doctors, which could include screening.

About half of the men receiving usual care ended up getting screened at some point.

Some of the men had complications for the prostate cancers that were found, Miller said. These include impotence and incontinence.

The European study tracked 162,243 men, age 55 to 69, and found a screening program reduced deaths by 20 per cent or seven deaths per 10,000 men screened.

Men in the European study were generally offered screening every four years or they got none. They were followed for an average of nine years.

The European researchers noted a high risk of overdiagnosis — the finding and treating of cancers that didn't threaten lives.

They concluded that 48 additional men would need to be treated to prevent one death from prostate cancer.

Screening in Canada

"My interpretation of the two studies together is that PSA screening likely does save some lives but does significant more harm," said Dr. Otis Brawley, the American Cancer Society's chief medical officer.

Canada does not have an organized PSA screening program. The $30 test is covered in most provinces, though B.C., Alberta and Ontario will pay for it only for men with a higher risk.

Bob Shiell of Calgary, who heads a support group called the Canadian Prostate Cancer Network, rejected the idea that screening does not save lives.

"We recommend that men get a benchmark test at age 40 and then annually or semi-annually get follow-up tests and track the results themselves," he said.

Some men playing recreational hockey in Toronto said they follow the group's advice.

"Last check-up, I asked the doctor, and he said, 'Not yet,' but I kind of insisted on it," said Rick Dicecco.