October 27, 2014 / 8:30 PM / in 3 years

Canadian guidelines recommend against prostate cancer test

(Reuters Health) - Men should not get a common blood test to screen for prostate cancer, according to new healthcare guidelines from Canada.

The potential for harm after prostate-specific antigen (PSA) testing outweighs the benefit, says the Canadian Task Force on Preventive Health Care.

“The ratio seems to be on the harm side - not the benefit side,” said Dr. Neil Bell, a member of the Task Force and chair of its prostate cancer screening working group.

The Canadian group is part of a growing list of medical organizations that either question or don’t recommend the test, which looks for elevated levels of a protein produced by the prostate gland.

The government-backed U.S. Preventive Services Task Force does not recommend PSA screening for prostate cancer. Additionally, the American College of Physicians does not recommend PSA screening among men younger than age 50 and older than age 69. Also, it says men ages 50 to 69 should be told about the “limited potential benefits and substantial harms” of screening before being offered the test.

Prostate cancer is the most common non-skin cancer among men and the third leading cause of cancer-related death among men, but the Task Force writes in the Canadian Medical Association Journal that the lifetime risk of prostate cancer death is only about 4 percent.

“The most typical feeling most people have is, ‘If I diagnose cancer early and I treat it, I get a better outcome,’” Bell said. “For prostate cancer, that doesn’t hold for a number of reasons.”

Specifically, most prostate cancers would never cause men to die or feel sick, said Bell, who is also a family physician and professor at the University of Alberta in Edmonton.

He and his colleagues write that about 70 percent of men between ages 70 and 79 are found to have undiagnosed prostate cancer after they die.

The new guidelines are based on a review of medical evidence related to PSA testing.

Overall, they found strong evidence showing that men would likely experience more harm than benefit from PSA screening if they're younger than 55 or older than 70.

The researchers say that for every 1,000 men between ages 55 and 69 screened using PSA, one will be saved from death by the test.

Of the other 999 who get screened by PSA, 720 will test negative. Of the 280 who will test positive, 178 will get additional testing - such as invasive biopsies - that ultimately show they don’t have cancer.

Of the 102 correctly diagnosed with prostate cancer by the PSA screening, 33 will be diagnosed with cancer that would not have caused them to become ill or die and end up with complications related to their treatment. Five men will die regardless of whether they get PSA screening.

“Available evidence does not conclusively show that PSA screening will reduce prostate cancer mortality, but it clearly shows an increased risk of harm,” they write. “The task force recommends that the PSA test should not be used to screen for prostate cancer.”

In an editorial, the University of Toronto’s Dr. Murray Krahn argues that doctors should not take away the choice of PSA testing from men.

“There clearly is not enough evidence to mount an organized screening program,” he writes. “However, the falling overall mortality in some countries that screen intensively, the evidence that treatment may have a very modest disease-specific mortality benefit, and the highly variable preferences for treatment outcomes suggest to me that we should not push patients out of decision-making in this area.”

The Task Force does write in its recommendations that some men may place more value on a small reduction in the risk of death and not be as concerned with the possible harm of the screening. Those men may choose to be screened, they write.

“There are some men who may want that benefit,” Bell said.

SOURCE: bit.ly/ZUJW6k and bit.ly/ZUJQvu CMAJ, online October 27, 2014.

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