|
Screening has been defined as "the examination of asymptomatic
people in order to classify them as likely or unlikely to have a
disease".1 When public health
authorities recommend screening for otherwise healthy people they
assume a substantial degree of responsibility. Clear evidence
should exist that the disease in question can be identified at an
earlier and more treatable stage in its natural history. Moreover,
the resulting fall in morbidity or mortality should be achieved
without too great a burden of adverse effects. In particular, the side
effects of the procedures necessary to establish a diagnosis and
those associated with the treatments employed should not be
excessive.
Screening for prostate cancer has spurred considerable
controversy, particularly since the introduction of
prostate-specific antigen (PSA) testing.2,3 Most authorities within
Australia and other countries recommend against such
testing.4 The reasons include a lack of
confidence that present interventions improve the prognosis of
lesions discovered at screening. Furthermore, the interventions
available (surgery and radiotherapy) are associated with a fairly
high frequency of impotence and incontinence.5 These may be a
high price to pay in the absence of proven benefit.
Negative sentiments about routine prostate cancer screening have
been incorporated into guidelines by four Australian
bodies.6-9 In this issue of the
Journal, Girgis et al examine the impact of such
guidelines on the behaviour of general practitioners faced with a
58-year-old man requesting screening at the behest of his
wife.10 They found that 90% of
respondents would accede to the patient's request. After being
acquainted with the Australian guidelines, three-quarters of the
respondents would still choose to test the patient. Only 15% of
respondents were confident that the guidelines would assist their
case if a patient whom they had refused to test subsequently developed
prostate cancer and sued. Few believed that they were at risk of being
sued if patients suffered complications of investigation or
treatment of which they had not been warned before screening.
The authors conclude that evidence-based guidelines have little
influence on GPs' approach to prostate cancer screening and raise the
issue of "more deliberate implementation". They also regard the lack
of confidence in a legal defence derived from national
evidence-based guidelines as troubling and recommend that steps be
taken to clarify their legal standing. As readers of the discussion in
the Journal's Internet peer review trial would be aware,11 these
conclusions have been challenged and have raised fundamental
questions about the nature of screening and the exact clinical
scenarios to which screening guidelines apply.
In practice, screening can be carried out in a variety of settings.
These range from organised mass population screening to advice
provided to a single patient presenting to a doctor on account of some
other problems (the latter is referred to as case finding). The common
feature is that the medical profession has taken the initiative to
promote the testing, and most screening guidelines have been
developed with this implicit assumption.
If this view is accepted, then a request by a patient to have a PSA test
would not qualify as screening. When the request has been made by an
asymptomatic patient without any particular concerns, the
risk-benefit ratio is likely to be similar to that of a typical
screening scenario, and it would be appropriate to be guided by the
same advice. In other words, in a setting strictly as described by
Girgis et al, where the patient requested testing at the suggestion of
his wife, it might well be appropriate to be guided by the same
published guidelines for prostate cancer screening. If special
concerns about the presence of prostate cancer have led to the
request, a GP might reasonably conclude that the extra component of
reassurance is sufficient to justify the test. However, men with
uncomplicated lower urinary tract symptoms should be advised that
there are no data to suggest that they are at increased risk of prostate
cancer.9
In real life clinical practice other complexities may also arise and
must be taken into account. When patients seek PSA testing, simple
refusal is rarely an option for GPs wishing to successfully balance
their varied roles of therapist, educator, friend, small
businessman and guardian of the public purse. Most GPs would agree
that their principal task is to provide a balanced account of the pros
and cons of testing. This would include the fact that a positive test
could initiate a potentially costly chain of events that might leave
the person incontinent and/or impotent without improving his life
expectancy. If these facts have been conveyed accurately and the
patient still requests testing then continued refusal may be seen as
unreasonable and paternalistic. For a simple screening
investigation such as PSA, where controversy is known to exist, it is
difficult to be critical of practitioners who would provide testing.
The other key issue raised by Girgis et al is the extent to which
defensive medicine influences the use of clinical investigations in
Australia. The fact that 46% of GPs perceived a medicolegal risk if
they failed to accede to the patient's request, despite being
presented with evidence that the testing was inappropriate,
illustrates the extent of this problem. It has been anticipated that
the provision of clinical practice guidelines might assist
practitioners dealing with controversial clinical problems by
providing a legally defensible approach with which to manage
patients. However, this study suggests that, at least in the case of
prostate cancer screening, guidelines do not provide this
reassurance. The authors point out that, unless the legal standing of
guidelines can be clarified, they are unlikely to provide a useful
response to the problem of defensive medicine.
Like many vigorous controversies, the arguments about prostate
cancer screening result from a lack of evidence of value rather than
evidence of no value. The definitive information to guide
practitioners will be derived from clinical trials large enough to
establish the balance of benefits and costs in a population. Trials of
this type are presently under way in both the United States and
Europe.12,13 Findings are expected
in 2002 or sometime thereafter. If these provide an unequivocal
result, then the response of practitioners to various testing
scenarios will be guided by much firmer evidence.
John J McNeil
Professor, and Head, Department of Epidemiology and Preventive
Medicine
Monash University, Melbourne,VIC
Paul E O'Brien
Professor, Department of Surgery
Monash University, Melbourne,
VIC
- Mornson AS. Screening. In: Rothman KJ, Greenland S, editors.
Modern epidemiology. Philadelphia: Lippincott-Raven, 1998; 499.
-
Mulley AG, Barry MJ. Controversy in managing patients with
prostate cancer. Banish dogma, get more data [editorial]. BMJ
1998; 316: 1919-1920.
-
Woolf SH. Screening for prostate cancer with prostate-specific
antigen -- an examination of the evidence. N Engl J Med 1995;
333: 1401-1405.
-
Feeney T. To screen or not to screen. In: Fundamentals of prostate
cancer detection and treatment [web site].
<http://rattler.cameron.edu/ww/index.html>. Revised 27
January 1999. Accessed 1 September 1999.
-
Coley CM, Barry MJ, Fleming C, et al. Early detection of prostate
cancer. Part II: Estimating the risks, benefits, and costs. Ann
Intern Med 1997; 126: 468-479.
-
Australian Cancer Society. Prostate cancer screening:
guidelines for health professionals. Cancer Forum 1995; 19:
47-50.
-
Australian Health Technology Advisory Committee. Prostate
cancer screening. Canberra: AGPS, 1996.
-
Royal Australian College of General Practitioners. Guidelines
for preventive activities in general practice. 4th ed. Sydney:
RACGP, 1996; 26.
-
National Health and Medical Research Council. Clinical practice
guidelines. The management of uncomplicated lower urinary tract
symptoms in men. Canberra: Commonwealth of Australia, 1997.
-
Girgis S, Ward JE, Thomson CJH. General practitioners'
perceptions of medicolegal risk. Using case scenarios to assess the
potential impact of prostate cancer screening guidelines. Med J
Aust 1999; 171: 362-366.
-
Girgis S, Ward JE, Thomson CJH. Potential impact using case
scenarios of guidelines discouraging prostate cancer screening on
general practitioners' perceptions of medicolegal risk [second
revised version with peer review discussion].
<http://www.mja.com.au/public/issues/iprs2/girgis/girgisframe.html>.
Accessed 1 September 1999.
-
Kramer BS, Brown ML, Prorok PC, et al. Prostate cancer screening:
what we know and what we need to know. Ann Intern Med 1993; 119:
914-923.
-
Auvinen A, Tammela T, Stenman U-H, et al. Screening for prostate
cancer using serum prostate-specific antigen: a randomised
population-based pilot study in Finland. Br J Cancer 1996;
74: 568-572.
©MJA 1999
Make a
comment
Readers may print a single copy for personal use. No further
reproduction or distribution of the articles
should proceed without the permission of the publisher. For
permission, contact the
Australasian Medical Publishing Company.
Journalists are welcome to write news stories based on what they read here, but should acknowledge their source as "an article published on the Internet by The Medical Journal of Australia <http://www.mja.com.au>".
<URL: http://www.mja.com.au/>
©1; 1999 Medical Journal of Australia.
We appreciate
your comments.
|
