Screening, case finding and evidence-based guidelines

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

1. Mornson AS. Screening. In: Rothman KJ, Greenland S, editors. Modern epidemiology. Philadelphia: Lippincott-Raven, 1998; 499.
2. Mulley AG, Barry MJ. Controversy in managing patients with prostate cancer. Banish dogma, get more data [editorial]. BMJ 1998; 316: 1919-1920.
3. Woolf SH. Screening for prostate cancer with prostate-specific antigen -- an examination of the evidence. N Engl J Med 1995; 333: 1401-1405.
4. 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.
5. 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.
6. Australian Cancer Society. Prostate cancer screening: guidelines for health professionals. Cancer Forum 1995; 19: 47-50.
7. Australian Health Technology Advisory Committee. Prostate cancer screening. Canberra: AGPS, 1996.
8. Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice. 4th ed. Sydney: RACGP, 1996; 26.
9. National Health and Medical Research Council. Clinical practice guidelines. The management of uncomplicated lower urinary tract symptoms in men. Canberra: Commonwealth of Australia, 1997.
10. 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.
11. 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.
12. 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.
13. 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.

&copy1; 1999 Medical Journal of Australia.