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A trial looking at a single blood test for prostate cancer (CAP)
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This trial was done to see if inviting men to have a single PSA blood test would reduce the number of men dying from prostate cancer. It was supported by Cancer Research UK.
More about this trial
Prostate specific antigen (PSA) is a protein that is often raised in men who have prostate cancer. But PSA levels can also be raised for many other reasons. Some men don’t have cancer even though they have a raised PSA level. And some men with prostate cancer don’t have a raised PSA level.
Many men whose cancer is diagnosed from a PSA test have low risk cancers. These cancers are likely to be slow growing and may not cause any problems during a man’s lifetime. But some men have a high risk cancer that will cause problems if it’s not treated.
Researchers want to find out if measuring PSA can be used as a screening test. Screening means testing people for early stages of an illness before they have any symptoms. When this trial was done there was no screening programme for prostate cancer for men in the UK.
In this trial, the research team wanted to find out if doing a single PSA blood test for men aged 50 to 69 would help detect high risk cancers earlier. And if treating these cancers earlier would mean that men would live longer.
As part of the trial, some men were offered a PSA test and some men weren’t, although they could have the test if they asked for it.
The aim of the trial was to see if an invitation to a have a single PSA test would reduce the number of men dying from prostate cancer.
Summary of results
This trial showed that there was no benefit in introducing a screening programme that offered a single PSA blood test. The one off test did mean that more men were diagnosed with prostate cancer. But it didn’t reduce the number of men dying from prostate cancer after an average of 10 years.
This trial recruited over 400,000 men who had not been diagnosed with prostate cancer. The men taking part were put into 1 of 2 groups at random, and:
- just under half were offered a PSA blood test
- just over half were not offered a PSA test, but could have one if they asked for one (this was the control group)
The men who were offered the PSA test were invited to a see a nurse to get more information and discuss the test. They then decided if they wanted to have the test or not. More than 70,000 men attended the clinic appointments. And more than 60,000 men decided to have the PSA blood test.
The PSA level was raised in around 7,000 men, and just under 6,000 of these men went on to have a biopsy of their prostate. More than 4,500 of these men were diagnosed with prostate cancer.
The research team compared how many men in the 2 groups were diagnosed with prostate cancer. Out of every 1,000 men it was:
- 43 men in the group who had been offered a PSA test
- 36 men in the control group who were not offered a PSA test
They found that the men who were diagnosed with prostate cancer after having the PSA test as part of the trial, were more likely to:
- be younger when they were diagnosed
- have cancers that were low risk
- have cancer that had not spread
So it was more likely that they had cancer which wouldn’t need treatment or cause problems during their lifetime.
The research team also looked at the number of men in each group who had died because of prostate cancer after an average of 10 years. They found it was 3 out of every 1,000 men in each group.
This trial showed that more men who had a one off PSA test were diagnosed with low risk prostate cancer that would probably not cause harm or need treatment. And that having a one off PSA test didn’t reduce the number of men dying from prostate cancer.
The trial team concluded that there is no benefit in screening for prostate cancer using a single PSA test.
We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (
How to join a clinical trial
Prof Richard Martin
Cancer Research UK
Department of Health
University of Bristol
University of Cambridge
University of Oxford