Issue 14 / 22 April 2013

WHEN a new pharmaceutical product hits the market, we expect regulators and professional bodies to be rigorous in assessing its safety and efficacy before any recommendation is made to patients.

But screening tests? Not so much.

Perhaps it’s natural that people are instinctively more worried about substances they put into their bodies than they are about tests that, after all, are simply going to give them information.

Except it really isn’t that simple, especially when it comes to a deeply flawed tool like the prostate-specific antigen (PSA) test used to predict men’s risk of developing prostate cancer.

The PSA test has been dividing medical opinion for more than a decade, as witnessed by reader comments on a recent MJA InSight column by Dr Michael Gliksman.

And who can forget the uproar when Professor Alan Coates, then president of the Cancer Council, went public with his decision not to have the test in 2003 based on his belief that the risks outweighed the benefits.

Advocates of screening — including medical professionals — often point to cases where the test could reasonably be said to have saved an individual man’s life by leading to early diagnosis of an aggressive cancer.

Yet, on a population level it’s not hard to mount an argument that the test does more harm than good.

New guidelines released this month by the American College of Physicians (ACP) recommend against the test unless the patient expresses a clear preference for it after discussion with his doctor — a discussion that would include being informed about “the limited potential benefits and substantial potential harms of prostate cancer screening”.

This issue has been bedevilled for years by conflicting guidelines that have failed to provide clear advice to either patients or clinicians, something the ACP set out to address.

In Australia, the NHMRC is conducting an independent evaluation of the evidence to help GPs and other health practitioners provide consistent, evidence-based advice to patients.

That’s all good, but it leaves the question of how this test came to be widely used, given the lack of evidence that the benefits outweigh the harms.

It’s hard to imagine a cancer drug being as widely prescribed if large trials had found no evidence it reduced mortality, while associating it with calamitous side effects such as incontinence and erectile dysfunction in a substantial minority of those treated.

Yet that seems to be pretty much the situation with the PSA test, at least in relation to asymptomatic men with no familial risk factors.

Dr Mitchell Katz, a primary care physician and director of the Los Angeles County Department of Health Services, wrote in JAMA Internal Medicine last week, asking why services such as his continue to offer the test.

Dr Katz is sceptical even about suggestions the decision should be left to the patient after discussion with his physician.

“Should we be offering our patients a menu of ineffective interventions on the idea that they are better able than we are to determine effectiveness”, he asks.

In his search for an understanding of the persistence of the PSA test, Dr Katz suggests most doctors want to “make their own decision on the basis of available evidence, even in fields in which they are not necessarily expert”.

“Is this a particularly noble aspect of our profession (doing what we believe even if the experts disagree)”, he wonders. “Or a kind of arrogance (yes, the … experts recommended against this test, but I know better? Or is it both?”

Provocative questions. But I think there is another question worth asking: should screening tests have to meet the same standard of evidence as any other medical intervention?

Jane McCredie is a Sydney-based science and medicine writer.

Posted 22 April 2013

9 thoughts on “Jane McCredie: Double standards

  1. John Parkinson says:

    What possible harm could come from taking a few drops of blood for a PSA? I had the test annually for years. When it became elevated cancer was confirmed by biopsy. My urologist now treats it most effectively by keeping a graph of my PSAs! At a certain point we will start hormonal suppression. Three cheers for the PSA!

  2. martin bailey says:

    I order PSA whenever a patient requests it- not for medical but for legal reasons, as I am sure most GPs do. Imagine if you talked a patient out of it, and he subsequently was found to have prostate cancer. PSA testing is like motherhood, or travel vaccinations; it is very hard to be against it.

  3. Dr. ARC says:

    I agree with the sentiments of Drs. Parkinson & Bailey. I have had a PSA test annually for many years to exclude the possibility of prostate disease. I’m happy to say that it has remained constant over this time and gives me a great deal of peace of mind.
    Much has been written about the PSA test doing more harm than good and when you find out why this is so it is because the interpretation of the test results lead on to other more invasive tests and surgical intervention, not due to the test itself.
    More specific tests relating to PSA blood levels are available (see http://www.cancer.gov/cancertopics/factsheet/detection/PSA ) and these should be used before surgical intervention.
    Whilst retired from medicine, my own doctor still sees the need for regular PSA testing and I wholeheartedly agree with him and recommend it to all general practitioners.

  4. Dr G says:

    I often wonder what the level of scientific evidence was in the early days when the decision to initially introduce breast screening was made and to suggest that even today that breast screening does not cause significant anxiety in patients generally and particularly in those that are requested to represent to have additional mammograms and additional tests such as biopsies etc makes one wonder why prostate screening has become such a political/ scientific hot potato.

  5. Dr Brian Parker says:

    Is Jane McCredie a medically trained doctor ? It seems extraordinary to me that these articles critising PSA testing are usually written by females !!!!!

  6. Dr Michael Gliksman says:

    The problem here (I think) is the gendered selectiveness in perception of net merit applied to prostate cancer screening vis a vis breast cancer screening.
    The study into ‘Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England’ (J Med Screen. 2010 March; 17(1): 25–30) reported that:A substantial and significant reduction in breast cancer mortality was associated with screening in both the Two-County Trial (P < 0.001) and the screening programme in England (P < 0.001). The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 from the Two-County Trial and screening programme in England, respectively.
    ie: 20,000 person years of reasonably targeted screening to save between 5-9 lives, and this before any account is taken of the impact of false positives on women’s lives.
    These figures are remarkably similar as for PSA screening, yet they lead to diametrically opposite conclusions based on nothing more than gender.
    I feel another article coming on…

  7. Brian Parker says:

    This morning I showed this article to a friend who is 74. It is interesting that he misinterpreted it, that having a PSA test would make him incontinent. This is just one example of the effect of misleading information on this subject of PSA testing. It is my view that all males over age 55 should have annual PSA tests and a digital examination of their prostates by their GP, especially if there is a family history of carcinoma of the prostate.

  8. Anonymous says:

    A 64 years old professional with malignant prostate cancer I saw recently told me that he was suing his previous GP because he was told repeatedly that “PSA screening did more harm than good”. This is the reality in GP land.

  9. Dr Joe says:

    All medical interventions carry risks and this includes testing in general and screening tests in particular. Harm does occur from false results and this harm is not insignificant. People need to know the facts and can then make a choice. Emotive terms like “life saving tests” would not be allowed if this was any other industry. The ACCC would strike them down.
    And yes this needs to apply to all screening tests including mammograms

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