Editorials

Should we screen for prostate cancer?

Routine screening for any condition is unwarranted without evidence that the test accurately detects early disease, that early detection improves outcomes, and that benefits outweigh harms. Unfortunately, such evidence is lacking for prostate cancer.

Although the test for prostate specific antigen (PSA) has reasonable sensitivity, it produces false positive results in two thirds of asymptomatic men.¹ About a third of tumours detected by the test are localised and more likely to progress, but there is no good evidence that treatment improves outcomes.¹ Moreover, the complications from screening and treatment may offset the potential benefits. Two recent reviews commissioned by the NHS Health Technology Assessment programme^{2 3} and a summary by the NHS Centre for Reviews and Dissemination⁴ came down against routine screening for prostate cancer and discouraged purchasers from paying for it. The reports instead encouraged further research to evaluate its effectiveness.

Are these recommendations reasonable? The answer differs for populations and individuals. Deciding whether to screen a population requires an assessment of the benefits and harms to society. The average preferences of the population, rather than those of individuals, must be considered. Although some men might prefer to be screened, the interests of the majority should prevail. Other population concerns apply: it may be unethical to recommend potentially harmful interventions in healthy people, and since NHS resources are limited the public good may be better served by diverting resources to services of proved value. From the population perspective, the recommendations against screening and the call for better research are appropriate. Other countries have reached the same conclusions.^{5 6 7 8}

But do the reports, which call on general practitioners to discourage screening, provide good counsel for individual patients? Should a man who wants the prostate specific antigen test be told that it is inappropriate? If a patient does not bring up screening, should the doctor remain silent and let the omission pass? Should doctors who favour screening suspend their beliefs? Proponents of evidence based medicine might respond that the answer is obvious: patients should be advised against screening, and doctors who believe otherwise should be corrected.

But is this advice evidence based? To be sure, the benefits of screening are unproved, but lack of evidence of effectiveness does not prove ineffectiveness. Although the harms of screening and treatment are known, without information on benefits we cannot know which outcome prevails. To tell all men that screening causes net harm is no more evidence based than claiming it is beneficial. That screening might reduce mortality remains a plausible hypothesis, unrefuted until a proper randomised trial is completed. Prostate cancer is the third leading cause of cancer deaths in British men (10 000 deaths annually). If the potential for screening to save lives remains unrefuted, do not men have a right to know about it? Should not patients (who will face the consequences of being or not being screened) be informed of their options and allowed to choose for themselves?

Patient empowerment generates several concerns. Firstly, some might argue that it invites patients to request any intervention irrespective of its effectiveness or safety. But shared decision making should be reserved for situations in which the superiority of one option over another is uncertain and depends on patient preferences. If modelling studies are to be believed, whether prostate screening results in net harm or good depends largely on the values patients place on different aspects of quality of life.⁹ Which choice is "right" or "wrong" for an individual turns on personal preferences.

Secondly, requests for screening could burden the NHS, threatening resources for other patients and more effective care. Of course, the NHS need not cover screening if it is not considered cost effective; patients who want testing could pay for it themselves. Moreover, the concern that empowering patients would drive up use may be unwarranted. Studies find that educating patients about the benefits and limitations of the prostate specific antigen test reduces rather than promotes requests for the test.^{10 11}

Thirdly, free choice could be awkward for doctors. Patients who want to be screened force doctors to confront their competing responsibilities as patient advocates and as stewards of societal resources. Doctors working in areas where health authorities have an official position against prostate cancer screening can escape this dilemma by blaming the policy on the authority. However, most general practitioners will have to decide for themselves whether to offer screening under the NHS. They must fulfil both responsibilities: as caregivers, they must encourage patients to choose what is best for them; as gatekeepers, they must explain that the NHS cannot afford the service. The positions are awkward but compatible.

Fourthly, busy doctors lack the time for long talks with patients, and the outcomes data they should discuss are poorly known. Other problems with shared decision making are reviewed elsewhere.¹² Fortunately, the NHS Centre for Reviews and Dissemination has prepared a patient education leaflet for just this purpose.¹³ It reviews the facts about screening, giving data on the likely outcomes of each option to help patients make more informed decisions.

The Health Technology Assessment programme's report wisely steers Britain away from a repetition of the United States' experience, where the introduction of uncontrolled prostate specific antigen screening spawned a prostate cancer "epidemic," a sharp rise in biopsies and prostatectomies, and the establishment of a new standard that makes curtailment of screening unlikely for medicolegal and ethical reasons.¹⁴ Whether the American approach will lower mortality and offset the rise in iatrogenic complications remains to be seen. Until compelling evidence becomes available, healthcare systems have good reason to defer prostate screening in lieu of other priorities. But individual doctors must also fulfil their responsibilities to patients. Men aged over 50 have a right to know about screening, regardless of whether the NHS funds it, and to decide for themselves which option to pursue. Whether patients will (or can) act on the information bears little on this duty.

Steven H Woolf, Associate clinical professor ^a

^a Department of Family Practice, Medical College of Virginia, Fairfax, VA 22033, USA (shwoolf{at}aol.com)

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