Mass screening for prostate cancer doesn't save lives and probably causes more harm than good.
This conclusion defies popular intuition about the benefits of screening in general and the typical practice in the USA. Before examining the evidence it is worth a quick summary of why the popular intuition is wrong here and in many other areas of medical screening. Gerd Gigerenzer and his team reviewed what is known in depth in their paper: Helping Doctors and Patients Make Sense of Health Statistics. The paper should be compulsory reading for anyone discussing medical statistics.
One key conclusion (my emphasis):
We show that information pamphlets, Web sites, leaflets distributed to doctors by the pharmaceutical industry, and even medical journals often report evidence in nontransparent forms that suggest big benefits of featured interventions and small harms. Without understanding the numbers involved, the public is susceptible to political and commercial manipulation of their anxieties and hopes, which undermines the goals of informed consent and shared decision making.
This goes some way to explaining the difference between evidence and perception about screening.
More relevant to this answer, the article quotes Sir Muir Gray (Chief Knowledge Officer of the NHS):
All screening programmes do harm; some do good as well, and, of these, some do more good than harm at reasonable cost.
So what does the clinical evidence say about the balance of good and had and the number of lives saved by screening?
Expert recommendations have recently been turning strongly against screening. A news story in a recent BMJ reports that the US expert group has found against screening (my emphasis):
The prostate specific antigen (PSA) test should not be used to screen men for prostate cancer because it is unlikely to save lives and can cause harm, says an independent panel of experts.
The US Preventive Services Task Force, an independent body of 16 experts that evaluates evidence to grade devices and rank preventive services, announced its recommendation against prostate cancer screening of all US men on 7 October. In a statement it said that there was “moderate certainty that PSA-based screening for prostate cancer has no net benefit.”
Part of this conclusion derives from new long term studies recently published (this one from the BMJ in 2011 which concluded:
After 20 years of follow-up the rate of death from prostate cancer did not differ significantly between men in the screening group and those in the control group.
There have also been recent meta-anlyses of many of the earlier studies. Here is the conclusion from a BMJ review in 2010:
Six randomised controlled trials with a total of 387 286 participants that met inclusion criteria were analysed. Screening was associated with an increased probability of receiving a diagnosis of prostate cancer (relative risk 1.46, 95% confidence interval 1.21 to 1.77; P<0.001) and stage I prostate cancer (1.95, 1.22 to 3.13; P=0.005). There was no significant effect of screening on death from prostate cancer (0.88, 0.71 to 1.09; P=0.25) or overall mortality (0.99, 0.97 to 1.01; P=0.44). All trials had one or more substantial methodological limitations. None provided data on the effects of screening on participants’ quality of life. Little information was provided about potential harms associated with screening.
Conclusions
The existing evidence from randomised controlled trials does not support the routine use of screening for prostate cancer with prostate specific antigen with or without digital rectal examination.
A Cochrane review in 2009 comes to similar conclusions.
Note one of the problems in many studies (see italicised text in the above quote) is that potential side effects of over treatment are likely to be missed. This is significant as they are serious (see the Wikipedia article) and understating them is likely to understate the harm of screening.
Perhaps the best summary is given by the man who invented the test in a New York Times article in 2010:
I never dreamed that my discovery four decades ago would lead to such a profit-driven public health disaster. The medical community must confront reality and stop the inappropriate use of P.S.A. screening. Doing so would save billions of dollars and rescue millions of men from unnecessary, debilitating treatments.
So it seems safe to conclude that Prostate cancer Screening doesn't save lives and may cause significant harm.
