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A national task force that issues guidelines for doctors says PSA testing should not be used to screen men for possible prostate cancer because it can lead to more harms than benefit. (OLEG PRIKHODKO/iSTOCKPHOTO)
A national task force that issues guidelines for doctors says PSA testing should not be used to screen men for possible prostate cancer because it can lead to more harms than benefit. (OLEG PRIKHODKO/iSTOCKPHOTO)

ANDRÉ PICARD

Evidence, not emotion, should drive prostate cancer screening Add to ...

You know what would be great? If we had a test that could accurately predict if a man is at risk of developing prostate cancer, and when. Better still would be an intervention that would ensure the cancer would never arise and that it has no negative side effects.

But that’s not we have. We have imperfect tests and imperfect treatments.

So what’s a man to do, especially when even the experts are deeply divided?

This week, the Canadian Task Force on Preventive Health Care said physicians should stop using the PSA (prostate specific antigen) test for early detection of prostate cancer because it results in more harm than benefit. (The U.S. Preventive Services Task Force came to a very similar conclusion three years earlier. )What the recommendations say, in short, is that while the test will detect cases of prostate cancer early, which allows early treatment, if screening is done routinely, a lot of men will also be treated unnecessarily and suffer real harm.

Predictably, patient groups like Prostate Cancer Canada and physicians belonging to groups like the Canadian Urological Association reacted with outrage. They are convinced the PSA test saves lives, and that every man should be tested.

So, who is right?

If there was a simple answer to that question, this debate would not have been going on for years.

So let’s focus on one key issue: Mortality.

About 4,000 Canadians will die of prostate cancer this year, making it the third leading cause of cancer death in men, after lung and colorectal cancer. An estimated 23,600 cases of prostate cancer will also be diagnosed.

Since the PSA test came into use, in 1991 in Canada – before that, rectal exams were used to detect swollen prostates and still are – here’s what has happened :

  • The incidence of prostate cancer has increased. If you test more men, you will find more cancer; opponents of screening argue that many men derive no benefit, and actually suffer much harm, from diagnosis;
  • The survival rate has increased: About 95 per cent of men are alive five years after diagnosis; but, again, that follows if many patients did not need treatment.
  • Mortality rates have dropped; what we don’t know is how much of that is due to early detection and how much is due to better treatment.

Large, long-term studies in Europe show that PSA screening reduces cancer mortality by less than one per cent.

Put another way, to prevent one death from prostate cancer, 1,055 men would need to be screened and 37 cancers detected.

The problem is that every man is convinced he is the man who was going to die. No one believes he would be harmed.

In response to the task force recommendations, there was an outpouring of moving testimonials from men for the lifesaving benefits of PSA testing.

But, according to the data, for every man who benefits from PSA testing, 27 are harmed by unnecessary treatment – complications such as impotence, incontinence and higher risk of heart disease and osteoporosis (because many men get a hormonal treatment that deprives their body of androgens).

Implicit in the recommendations is the concern that, once a man is diagnosed, a cascade of interventions will follow. In an ideal world, initial PSA results would trigger little more than active surveillance , whereby the clinician does little more than monitor for symptoms.

We simply do not know what happens to individual patients after a PSA screening test raises concerns, although there is some evidence of over-treatment.

(To be clear, the PSA test is an excellent tool for monitoring patients who have cancer and are undergoing treatment. The debate revolves around its usefulness as a diagnostic tool. It generates a lot of false positives, because PSA levels can shoot up for reasons other than the presence of cancer.)

Prostate cancer can be extremely aggressive and kill quickly but, by and large, it is slow-growing. It is often described as a cancer you die with rather than of. But anecdote is much more powerful than statistics.

Almost all the 23,600 men diagnosed with prostate cancer this year will be convinced that testing saved their lifes.

The reality is a tad more complicated.

We have a lousy test, and physicians and their patients must decide how much stock to put in it.

The most dispassionate and sensible advice comes from the Canadian Cancer Society. It recommends men over 50 discuss the pros and cons of PSA testing with their physicians, and decide based on family history and personal risk tolerance .

To come to the right decision, patients and doctors must have a good grasp of the evidence, be willing to set aside emotion, and then go with their gut.

This corrects an earlier version that indicated Jack Layton died of prostate cancer.

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Follow on Twitter: @picardonhealth

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