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Clinicians should promote informed decision making while awaiting definitive evidence from RCTs
Current policies on screening for prostate cancer vary worldwide. This discrepancy can be explained in part by the lack of clear evidence to support or refute such screening. Evidence is lacking for the diagnostic accuracy of current screening tests (digital rectal examination and prostate specific antigen testing) and whether screening ultimately improves survival and quality of life.1 In their study in this week's BMJ, Lane and colleagues present results from the prostate testing for cancer and treatment study, which assesses the feasibility of testing for prostate cancer in younger men (45-49 years).2
A recent systematic review1 identified two randomised controlled trials (RCTs) assessing the effectiveness of screening for prostate cancer.3 4 Both trials had several methodological weaknesses. Reanalysis of these trials using an intention to treat analysis showed no significant reduction in mortality between men randomised to screening and men in control groups (relative risk 1.01, 95% confidence interval 0.76 to 1.33). The review concluded that these trials found insufficient evidence to support or refute screening for prostate cancer.
In the presence of such uncertainty further evidence from methodologically robust studies is needed to determine the effect of screening for prostate cancer on prostate cancer specific mortality, quality of life, potential harms, and costs. The results of several ongoing trials are awaited.5 6 7
Lane and colleagues report the uptake of prostate specific antigen testing, the positive predictive value of prostate specific antigen, and the clinical features of detected cancers in 442 UK men aged 45-49, using a prostate specific antigen age based threshold for biopsy of 1.5 ng/ml. They show that this group of men will accept testing for prostate cancer, albeit at a much lower rate than older men. Using this reference range, Lane and colleagues diagnosed prostate cancer in 10 of the 442 men. Five of these cases were classified as potentially clinically relevant.
Although this paper makes an important contribution to our knowledge of age specific prostate specific antigen thresholds in a white population in the United Kingdom, the final decision regarding widespread screening should be based on reliable population based data, preferably from high quality RCTs. Such data will provide strong evidence on the effects of screening on individual patient outcomes. As Lane and colleagues point out, the results of their paper, and others on age specific prostate specific antigen thresholds, should be interpreted with caution until results from ongoing RCTs determining the effects of screening at a population level are available.
In the absence of evidence to guide clinicians about whether or not to screen men for prostate cancer, many governing medical bodies currently recommend informed discussion between patient and doctor when contemplating screening for prostate cancer. But can a patient be truly informed if medical professionals and researchers are still investigating what the best course of action is? In cases such as this, evidence based practitioners place greater emphasis on the clinician's experience and the patient's values to facilitate informed discussion and decision making.
Lack of knowledge, limited access to high quality educational materials, and psychosocial attitudes may all act as barriers for men when seeking and participating in discussion with clinicians about screening for prostate cancer.8 These factors may all increase conflict in making decisions or uncertainty associated with treatment.8 A systematic review of decision aids for people facing screening and treatment decisions found that decision aids increased consumer knowledge, lowered conflict when making decisions, and promoted greater agreement between patient values and the final decision.9
Screening for prostate cancer is now commonplace in many settings, despite the lack of evidence from ongoing randomised controlled trials. The paper by Lane and colleagues provides useful information on the prevalence of prostate cancer and diagnostic accuracy of different screening tests. It is also beneficial to understand the acceptability of prostate cancer screening in younger men, because this adds to the growing body of literature on patient preference and may be useful when planning ways to promote the uptake of screening. However, as Lane and colleagues point out, such data will be most useful if the ongoing randomised controlled trials show that screening for prostate cancer is effective.
Clinicians and consumers currently stumble through the darkness that pervades the debate on screening for prostate cancer. Until the results of ongoing RCTs can shed light on this important clinical and policy decision, we recommend informed discussion between clinicians and patients about the benefits, potential harms, and limitations of screening. Greater uptake of patient education and decision aids, and incorporation of the clinician's experience and expertise, may help overcome the barriers to discussion and facilitate an informed decision.
This article was published on bmj.com on 15 November 2007
Competing interests: SG is the director of the Australasian Cochrane Centre and a member of the Cochrane Collaboration steering committee. DI and SG have received funding from Andrology Australia, which is a community and professional education programme funded by the Australian government that provides health information on male reproductive health.
Provenance and peer review: Commissioned; not externally peer reviewed.