Now Canada Says Don't Use PSA Test for Cancer Screening

Zosia Chustecka

October 27, 2014

The Canadian Task Force on Preventive Health Care has released updated guidelines that say the prostate-specific antigen (PSA) test should not be used to screen for prostate cancer. This recommendation is based on evidence that shows an increased risk for harm and uncertain benefits, and it applies to all men (all those without a previous diagnosis of prostate cancer).

The new guideline is published online October 27 in the Canadian Medical Association Journal.

These updated Canadian guidelines are consistent with the latest recommendations from the US Preventive Services Task Force and the Cancer Council Australia, the task force notes.

It adds that the United Kingdom does not have an organized screening program but recommends that men concerned about the risk for prostate cancer receive balanced information on the benefits and harms of screening.

Evidence Shows "Increased Risk of Harm"

The new Canadian guidelines update those issued in 1994, are based on systematic evidence reviews, and use an international framework for assessing quality of evidence and the strength of recommendations for clinical guidelines (Grading of Recommendations Assessment, Development and Evaluation [GRADE]).

The task force reports that a literature review found six randomized clinical trials, but three of these were discounted because they were considered to have a high risk of bias. The following were considered: the European Randomized Study for Screening Prostate Cancer (ERSPC), using data from all sites, and the US Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO).

As previously reported by Medscape Medical News, the European trial found that PSA screening does reduce the risk of death from prostate cancer, but the US trial did not; however, the latter trial has been heavily criticized as flawed because many men in the control group also underwent PSA testing.

The Canadian Task Force concludes that "the available evidence does not conclusively show that PSA screening will reduce prostate cancer mortality, but it clearly shows an increased risk of harm."

It clearly shows an increased risk of harm. Canadian Task Force on Preventive Health Care

It elaborates on the potential harm by noting that for men with prostate cancer diagnosed through PSA screening, 11.3% to 19.8% will receive a false-positive diagnosis and 40% to 56% will be affected by overdiagnosis leading to invasive treatment. Treatment such as surgery can cause postoperative complications, such as infection (in 11% to 21% of men), urinary incontinence (in up to 17.8%), and erectile dysfunction (23.4%).

The recommendation not to use the PSA test for screening for prostate cancer applies to all men, the Task Force notes. It adds that this includes men who are considered to be high risk (eg, black men or 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 recommendation is "strong" for men who are younger than age 55 years and over 70 years of age, it notes. This means that clinicians should not routinely discuss screening in men within these age groups unless the patient himself raises the topic.

The recommendation is "weak" for men aged 55 to 69 years of age, the Task Force adds. The Task Force explains the implication of this: "Clinicians who believe that a patient places a high value on the small potential benefit of screening and is less concerned about the harms may wish to discuss the benefits and harms of screening with the patient, so that he can make an informed decision about whether to be screened."

To aid that discussion of potential harms and benefits, the Task Force has developed a decision-making tool. Other groups have also developed tools to help with making this decision.

However, the Task Force also adds: "Any use of PSA testing to screen for prostate cancer requires a thoughtful discussion between the clinician and the patient about the balance between unclear benefits and substantial harms."

What About Patient Preferences?

The new guideline is an "excellent example of health care decisions being made from the perspective of evidence-based medicine," but the Task Force "paid insufficient attention to patient values, patient preferences and costs," writes Murray Krahn, MD, MSc, from Toronto University, Ontario, Canada, in an accompanying commentary.

Both the Canadian and the US task forces have based their recommendations only on evidence from clinical trials, Dr Krahn writes. But other sources of evidence should also be considered, he argues.

The Canadian Task Force has provided a "good summary of the data on effectiveness of prostate cancer screening, and a reasonable review of the rate at which potential harms occur," he writes. "However, the review does not include a comprehensive review of patient harms: yes, they happen, but are they important?"

"The guideline gives only a brief nod to patient preference and shared decision making," he adds, and there is no review of cost because this is outside the task force's purview.

"There is clearly not enough evidence to mount an organized screening program," Dr Krahn comments.

"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," he says.

Disagreement From Advocacy Group

An immediate response from the advocacy group Prostate Cancer Canada highlighted its disagreement with the new guidelines. "When performed appropriately, the benefits of PSA screening far outweigh the negatives," the group said in a statement. It also cited a paper published recently in Cancer, based on modelling estimates, predicting that if PSA testing were eliminated, cases of metastatic prostate cancer would double, resulting in an estimated 13% to 20% increase in prostate cancer deaths annually.

"Prostate Cancer Canada believes PSA testing should be used as part of 'smart screening', a personalized approach where men are tested to establish a baseline number," the group explains. "Subsequent tests are performed to monitor any changes to the baseline. If a change is detected, the patient and his healthcare provider should discuss a course of action based on his personal risk factors. This could include other diagnostic procedures such as a digital rectal exam, biopsy or even an MRI."

The advocacy group says that prominent experts agree with its view, and it quotes Laurence Klotz, MD, chief of urology at Sunnybrook Health Sciences Centre in Toronto, saying: "We need to remove the association of the PSA test as a diagnostic for prostate cancer and instead regard it as a valuable predictor of risk."

"The PSA test is merely the first step in the process to detect prostate cancer in its earliest stages when there are more treatment options," Dr Klotz comments in a press release from the group. "While a single PSA test on its own will not diagnose prostate cancer, it is used as another variable to calculate an individual's personal risk of prostate cancer and allow for tailored clinical follow-up."

This isn't a black and white issue Dr. Stuart Edmonds

"This isn't a black and white issue," says Stuart Edmonds, PhD, vice-president of research at Prostate Cancer Canada. "You can't abandon testing when there's research out there that says it's useful, particularly in the absence of anything better. We believe that when the results are properly interpreted, the benefits of PSA screening outweigh the risks of not screening."

Funding for the Task Force is provided by the Public Health Agency of Canada and the Canadian Institutes of Health Research. The authors of the guidelines and Dr Krahn have disclosed relevant financial relationships.

CMAJ. Published online October 27, 2014. Abstract Commentary


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