From Dance with Chance blog:
The recent publication of two large-scale studies of prostate screening in the US and Europe attracted our attention. After all, (a) this was something we wrote about in our book, and (b) we are – all three of us – men of a certain age.
In the US study, 38,343 men received annual PSA (Prostate Specific Antigen) blood tests while 38,350 men were assigned to a control group. After 7 years of follow-up, the incidence of prostate cancer death per 10,000 person-years was 2% in the screening group – that is 50 deaths. In the control group it was 1.7%, or 44 deaths. Not particularly significant then.
The European study involved some 180,000 men. This time, however, the screening group was billed as having a 20.7% improvement in the survival rate over the control group. This seems impressive and a good reason for continuing with PSA screening – in Europe at least.
So are European doctors better at screening than their US colleagues? Or is it just that numbers can be deceptive?
There were 214 deaths from prostate cancer in the screening group and 326 in the control group. This means 112 fewer deaths in the screening group, or a relative improvement over the screening group of 20.7% – found by dividing 112 by 540 (540 = 214 + 326).
In absolute terms, however, the improvement is much less impressive, since there were 72,890 subjects in the screening group and 89,353 in the control group. This means 7.1 fewer deaths in the screening group than in the control group, for every 10,000 people. If we consider that the study lasted some nine years, this is a tiny improvement of less than one person per year.
So should society continue this kind of testing? The answer should depend on the costs as well as the benefits. The authors of the European prostate cancer screening study summarize them as follows: 1,410 men would need to be screened and 48 additional cases of prostate cancer treated to prevent one death from prostate cancer.
In addition, they say: of the men who underwent biopsy for an elevated PSA value, 13,308 (75.9%) had a false positive result. And the authors of the USA study talk about 68 complications (per 10,000 screened men) caused by the diagnostic process, including bleeding, clot formation, and urinary difficulties while the treatment complications, generally more serious, included infection, incontinence, impotence, and other disorders.
On a personal level, where does this leave the three of us? First, there’s the cost and inconvenience of having a blood test, which we can probably dismiss as insignificant. Second, there’s the possibility of being one of the 47 treated unnecessarily to save one life. That’s a bit more worrying. Third, there’s the chance of being one of the 68 in 10,000 who get serious side affects from the diagnostic process. Now, that really is starting to get serious. Finally, there’s the unpleasantness of the diagnostic process itself. Those 13,308 American men who underwent the biopsy by mistake not only had a thoroughly uncomfortable experience, but probably also had a traumatic time until the PSA test was proved wrong. At this point, we’re feeling ill just thinking about it.
So would you do the test?