Prostate cancer – to screen or not to screen

Executive summary

* A paper has just been published with updated results for the CAP trial.

* The CAP trial was a cluster randomised trial of PSA testing for prostate cancer. Approximately 400,000 men were analysed for the recent paper. They were recruited at 573 surgeries in England and Wales between 2002 and 2009. They were randomised by surgery to receive one invitation for a PSA test (the intervention group) or no invitation (the control group).

* This paper reported the 15-year follow-up results for deaths from prostate cancer. It found a slightly lower incidence rate of prostate cancer deaths in the intervention group. However, the 10-year follow-up and the 18-year follow-up found no difference for prostate cancer deaths.

* There was no significant difference in deaths from any cause (the measure that matters) for the 10, 15 or 18-year follow-ups.

* The diagnoses of prostate cancer were higher in the intervention group – multiples higher at 18-months and 10-year follow-up.

* Approximately one in six cancers were overdiagnoses. These would have been treated and treatment for prostate cancer can harm – incontinence and impotency being common outcomes.

* If being invited to a PSA test makes no difference to overall mortality and can unnecessarily harm, the question to screen or not to screen does not seem difficult to answer. There is a caveat.