10/27/2014 12:00 EDT | Updated 12/27/2014 05:59 EST

PSA test should be abandoned as screen for prostate cancer, task force says

The blood test mostly commonly used to screen men for prostate cancer should be dropped, because it does more harm than good, says a Canadian task force.

The prostate-specific antigen, or PSA, test measures inflammation that can be elevated for many reasons other than cancer, such as normal enlargement of the prostate with age or an infection.

Researchers said over-diagnosis occurs when cancer is detected correctly but would not cause symptoms or death.

The main problems are false-positive results and over-diagnosis, thereview indicated. A positive PSA test result often leads to more tests such as a biopsy, which carries risks of bleeding, infection, and urinary incontinence.

In most men with prostate cancer, the tumour grows slowly, and they’re likely to die of another cause before the prostate tumour causes any symptoms.  

Prostate cancer is the most commonly diagnosed non-skin cancer in men. The prognosis for most prostate cancers is good, with a 10-year survival rate of 95 per cent.

Screening aims to find cancer before symptoms appear and reduce the chance of dying from cancer with early treatment.

In Monday’s issue of the Canadian Medical Association Journal, the Canadian Task Force on Preventive Health Care reviewed the latest evidence and international best practice to weigh the benefits and harms of PSA screening with or without digital rectal exams.

"Available evidence does not conclusively show that PSA screening will reduce prostate cancer mortality, but it clearly shows an elevated risk of harm. The task force recommends that the PSA test should not be used to screen for prostate cancer," Dr. Neil Bell, chair of the prostate cancer guideline working group member, and his team concluded.

The guideline is aimed at physicians and other health-care professionals and policymakers. It updates the task force’s recommendation from 1994 on screening with the PSA test.

The new recommendations include:

- For men under age 55 and over age 70, the task force recommends not using the PSA test to screen for prostate cancer. This strong recommendation is based on the lack of clear evidence that screening with the PSA test reduces mortality and on the evidence of increased risk of harm.

- For men aged 55–69 years, the task force also recommends not screening, although it recognizes that some men may place high value on the small potential reduction in the risk of death and suggests that physicians should discuss the benefits and harms with these patients.

- These recommendations apply to men considered high risk — black men and those with a family history of prostate cancer — because the evidence does not indicate that the benefits and harms of screening are different for this group.

The key evidence from a well-done European study that showed inconsistent results, with a small potential positive effect over a long period of time balanced against the clear evidence of harm, said Dr. James Dickinson, a member of the prostate cancer guideline working group and a professor of family medicine at the University of Calgary.

"Fundamentally this is not a good enough test to be worth using," Dickinson said in an interview. "Let's hope that better things come in the future, but right now it's not worth using. It's more likely to cause harm than benefit."

A Canadian specialist, however, takes issue with the recommendation.

The task force’s guidelines are flawed for Canada, said Dr. Neil Fleshner, who studies and treats prostate cancer at Princess Margaret Cancer Centre in Toronto.

"By using the PSA test, we can absolutely find lethal cancers early and by intervening in those men, we can save their lives. Therefore, these recommendations undoubtedly will lead to more prostate cancer deaths," Fleshner said.

The task force said that separating screening from treatment through watchful waiting or active surveillance, could change the ratio of risks to benefits of PSA screening but the hypothesis needs to be tested.

The task force said it did not consider the costs of screening or treatment of prostate cancer.