Two studies this week demonstrate this principle. Firstly, results of a long-term trial of prostate cancer screening by PSA (prostate specific antigen) blood test. I summarised the study for BMJ news here and you can see the study itself here.
PSA testing saves some lives by diagnosing prostate cancer early enough to treat (about one life for every 780 men invited for screening in this study). The downside is that it over-diagnoses cancers, so many men have treatment for harmless tumours that wouldn’t have grown or caused symptoms in their lifetime. The side-effects of prostate cancer treatment can include sexual dysfunction and incontinence, so the potential for harm is clear.
What interested me was that the authors of the study accept the problem. Despite showing a clear benefit for PSA testing, they don’t call for universal adoption, but say that the medical profession must develop better ways to tell the difference between indolent, low-risk cancers and the aggressive types that kill. In the meantime, they say patients should be given enough information to decide for themselves whether to have a PSA test. It’s refreshing to see researchers giving patients credit for enough intelligence to make their own decisions. (Here’s a link to a patient decision aid on PSA testing that I helped to develop for the NHS).
The second study, which I reported for BMJ’s patient website Best Health here, looked at the effects of taking daily aspirin. The benefits are a reduction in the chances of getting and dying from some types of cancer (mainly colorectal), and of having heart attacks or strokes. The main risk of aspirin is bleeding in the gut or stomach, and stomach ulcers. The researchers crunched numbers from the latest studies on the effects of long-term aspirin use, and concluded that it helps more people than it harms, among those aged 50 to 65. They stopped short of making a recommendation about whether all over-50s should start taking aspirin. You can see the study here.
For the average Joe and Joanna, the question is all about risk. You feel like a healthy person. Do you take a screening test or a drug that might help you live longer and avoid disease in the future, but with a small chance of causing you harm in the here and now? Or do you decide to live for today and worry about the future when it happens?
With preventive medicine making advances all the time, it’s a choice we’ll all have to face more frequently in future.