Prostate-specific antigen testing for prostate cancer: the case for informed consent

Informed consent should be obtained before testing asymptomatic men

MJA 1998; 169: 9-10  

The prostate-specific antigen (PSA) test is only the first step in screening asymptomatic men for prostate cancer. Its lack of specificity usually necessitates transrectal ultrasound-guided multiple biopsies for confirmation of the diagnosis. These procedures will discover a large number of cancers, many of which, viewed from one perspective, will be potentially curable by surgery1 or radiotherapy. However, epidemiological evidence suggests that most cancers localised to the prostate will not cause clinically significant disease for at least 10 years.2 PSA-based screening presents unique difficulties because at present there is no means to distinguish those cancers which will impair health to a degree that justifies the risk of iatrogenic morbidity of investigation (biopsy-related sepsis) and curative treatment (incontinence, impotence, and radiation damage to adjacent organs). This issue of the Journal includes four pertinent articles: the incidence of prostate cancer and the prevalence of PSA testing are described and compared in Western Australia3 (Threlfall et al) and New South Wales4 (Smith & Armstrong); reasons for PSA tests being ordered by general practitioners (GPs) in central Sydney are reported5 (Ward et al); and the prevalence of PSA testing among South Australian men is given, together with findings concerning men's understanding of the immediate consequences of having a PSA test6 (Pinnock et al). PSA tests were the sixth most frequent pathology item ordered by GPs in the June quarter of 1996,5 but their use has fallen since the peak in 1995.3,4 This may indicate that GPs are adopting a more discerning approach, in line with guidelines that recommend against the use of PSA tests to screen for prostate cancer.7 However, in the period 1992-1996, it is clear that GPs and asymptomatic men adopted the test enthusiastically. Medicare data show that one in every four Australian men (27%) aged at least 50 years had a PSA test in 1995 or 19964 and, in a random survey of households in South Australia carried out in 1996, 28% of men aged 50 years or older without prostate cancer reported having a PSA test in the preceding 12 months.6 A high proportion of PSA tests were ordered by GPs for screening ("routine for age") or in response to patient request.5,6 Men over 70 years old have been tested as frequently as younger men4,6 -- but the older the man when prostate cancer is detected, the less likely it is that a benefit from early intervention is possible.8 In South Australia, there was an association between PSA testing and visiting a doctor for urinary symptoms.6 PSA testing is not recommended for men presenting with uncomplicated lower urinary tract symptoms (because such symptoms are unlikely to be indicative of localised prostate cancer),6,9 but it is understandable that GPs may order the test because the question of prostate disease has been raised during the consultation. It is evident that PSA tests have been carried out without the consequences of an abnormal test result being adequately explained.6 GPs need a clear-cut structured framework within which the paucity of good scientific evidence and the potential harms and benefits can be discussed with patients. Most GPs will have had difficulty reconciling the negative evidence relating to the cost-benefit of PSA testing with their natural inclination to detect and treat cancer at an early stage. However, in asymptomatic people the balance of harm versus benefit must demonstrably be more clearly in favour of benefit than in usual clinical practice. In the United States, where enthusiasm for both case-finding by PSA testing and treatment by radical prostatectomy occurred some years earlier than in Australia, there appears to have been a small fall in mortality from prostate cancer in the period 1990-1995.10 Interpretation of this fall is far from clear, but it may be attributable to the dramatic increase in use of radical prostatectomy11 or other therapeutic advances in the 1980s. Conclusive evidence of reduced mortality from prostate cancer as a result of PSA screening must await the completion of randomised controlled trials. From an intention-to-treat analysis of men aged 50-79 years with clinically localised prostate cancer in the population-based US Surveillance, Epidemiology, and End Results (SEER) Program, no advantage in 10-year disease-specific survival was found for either radical prostatectomy or radiotherapy compared with conservative management for men with tumours with a Gleason score of 2-4 (well differentiated).12 For men with tumours with a Gleason score of 5-7 (moderately differentiated) there was an advantage for radical prostatectomy but not for radiotherapy -- this may reflect the fact that patients selected for surgery excluded those whose general health, and therefore prognosis, was already bad when prostate cancer was diagnosed. The 10-year disease-specific survival was better for men with tumours with a Gleason score of 8-10 (poorly differentiated) treated by either radical prostatectomy or radiotherapy compared with conservative management. Because of the way screening for breast and cervical cancers has been promoted, the general public will perceive that finding a cancer earlier is beneficial because treatment is more likely to be effective. However, using the PSA test for detecting prostate cancer in asymptomatic men is not analogous to mammography for early detection of breast cancer in asymptomatic women. Apart from the unproven benefit, there is a need for universally applied guidelines for the management of men with an abnormal test result, comparable with those built into the mammographic screening program. Such guidelines would include counselling and provision for a multidisciplinary approach when a decision is being made about the best course of management. At present, the cascade of events following an abnormal PSA test result proceeds without the man always making an informed choice before the test. Indeed, when men are given prior information about the PSA test and its characteristics, the consequences of having a raised PSA level, follow-up diagnostic procedures, treatment options and side effects, they are less likely to decide to have the test.13 GPs have a professional responsibility to give appropriate advice based on current evidence and, where there is uncertainty, this should be conveyed. Obtaining informed consent is accepted in the context of an invasive procedure. Given the medical uncertainties, the invasive nature of the confirmatory and therapeutic procedures that will be required if the test is positive, and the possibility of doing more harm than good, informed consent should be obtained from asymptomatic men before ordering a PSA test. Margaret McCredie Professorial Research Fellow, Department of Preventive and Social Medicine University of Otago, Dunedin, New Zealand, and Cancer Epidemiology Research Unit, NSW Cancer Council, Woolloomooloo, NSW Brian Cox Senior Research Fellow, Department of Preventive and Social Medicine University of Otago, Dunedin, New Zealand Kaye KW. Prostate cancer: enthusiasm for screening. Med J Aust 1995; 162: 540-541. Johansson J-E, Adami H-O, Andersson S-O, et al. High 10-year survival rate in patients with early, untreated prostatic cancer. JAMA 1992; 267: 2192-2196. Threlfall TJ, English DR, Rouse IL. Prostate cancer in Western Australia: trends in incidence and mortality from 1985 to 1996. Med J Aust 1998; 169: 21-24. Smith DP, Armstrong BK. Prostate-specific antigen testing in Australia and association with prostate cancer incidence in New South Wales. Med J Aust 1998; 169: 17-20. Ward JE, Gupta L, Taylor NJ. Do general practitioners use prostate-specific antigen as a screening test for early prostate cancer? Med J Aust 1998; 169: 29-31. Pinnock CB, Weller DP, Marshall VR. Self-reported prevalence of prostate-specific antigen testing in South Australia: a community study. Med J Aust 1998; 169: 25-28. Australian Health Technology Advisory Committee. Prostate cancer screening. Canberra: AGPS, 1996. Fleming C, Wasson JH, Albertsen PC, et al. A decision analysis of alternative treatment strategies for clinically localized prostate cancer. Prostate Patient Outcomes Research Team. JAMA 1993; 269: 2650-2658. National Health and Medical Research Council. Clinical practice guidelines. The management of uncomplicated lower urinary tract symptoms in men. Canberra: AGPS, 1996. Mettlin CJ, Murphy GP. Why is the prostate cancer death rate declining in the United States? Cancer 1998; 82: 249-251. Lu-Yao GL, Greenberg ER. Changes in prostate cancer incidence and treatment in USA. Lancet 1994; 343: 251-254. Lu-Yao GL, Yao S-L. Population-based study of long-term survival in patients with clinically localised prostate cancer. Lancet 1997; 349: 906-910. Flood AB, Wennberg JE, Nease RF, et al. The importance of patient preference in the decision to screen for prostate cancer. Prostate Patient Outcomes Research Team. J Gen Intern Med 1996; 11: 342-349.