Download Prostate Cancer Screening: FAQs

Prostate Cancer Screening: FAQs
How common is prostate cancer in the UK?
It is now the commonest form of cancer diagnosed in men in the UK. This graph shows the number of
new cases found each year (incidence)
Prostate Cancer European Age-Standardised Incidence Rates, UK, 1975-20101
The incidence
appears to have
doubled in the last
20 years. This is
partly due to an
aging population
but also because
more cases are
being found.
Despite this, the
number of deaths is
falling.
Prostate Cancer European Age-Standardised Mortality Rates, UK, 1971-20102
If a cancer seems to
be becoming
commoner but the
number of deaths is
falling that could be
because treatments
have become a lot
better and/or
because many of the
new cases would not
have caused death if
left untreated.
There are probably many prostate cancers out there waiting to be discovered. A study in Detroit
published in 1996 looked at 525 men who had died in accidents. Their prostate glands were completely
removed and examined carefully for prostate cancer. The percentage in different age groups who were
found to have cancer of the prostate amongst white races is shown below3:
Age group
% with
cancer of
the prostate
20-29
8%
30-39
31 %
40-49
37%
50-59
44%
60-69
65%
70-79
83%
So the harder you look the more cancers you will find.
Is it true that screening involves a simple blood test?
Screening for prostate cancer is a two stage process. Firstly a PSA blood test is taken and the prostate
gland examined at the surgery. Prostate Specific Antigen is a chemical that is released by active prostate
tissue into the blood stream. The bigger the prostate the higher the level, and the more actively growing
cancer cells the higher the level. There are published levels for what is thought to be acceptable for
particular age groups, but these are arbitrary. If your level is higher than the recommended figure then
you will be referred to the hospital for further tests. Having a level higher than the figure does not mean
that you have a cancer, and having a level lower does not mean that you do not. It is simply a guide as to
who should be referred to the hospital.
What happens at the hospital?
The next stage is to collect some samples of prostate tissue by performing a biopsy. You have two
prostate glands, each about the size of a chestnut, that sit at the base of the bladder. They can be felt
and reached through the lining of the rectum. The biopsy process consists of taking a number of thin
cores of prostate tissue. The more cores are taken the more likely you are to have a cancer found. For a
small cancer it is a bit like trying to shoot at a target in the dark. Sometimes the target is missed. About a
third of people have side effects from the procedure such as pain, bleeding or infection 4,5.
These cores are examined under the microscope to look for cancer cells. You might have a scan as well.
Then the results are reviewed with you and if cancer is found the treatment is discussed. It is not always
clear what the best form of treatment will be.
Why have I not been invited for a PSA test?
There is no official prostate screening programme in the UK. All potential screening programmes are
looked at in the UK by the National Screening Committee who decide if it is worthwhile. For example the
committee felt that it was right to set up a bowel cancer screening programme so this has been done.
They did not feel that there was enough evidence of benefit to set up a national prostate screening
programme.
How many lives does screening save?
There have been a number of large studies in recent years looking at the benefits of screening. The
results do not always agree. For example a trial in the US that looked at nearly 80,000 people found a
higher death rate in those who had been screened than those who had not been. Recent reviews in the
USA4 and the UK5 have looked at the evidence. They looked at men aged 55-69 who had a blood test
every 1-4 years for 10 years. They found that the 10 year risk of dying from prostate cancer without
screening was about 5 in 1000. With screening this dropped to 4 to 5 per 1000. So the number of men
who avoided prostate cancer death was between 0 and 1 per 1000.
What is the likelihood of having a raised PSA level or being diagnosed with cancer with screening?
The same reviews estimated that the chance of being diagnosed with prostate cancer during the 10
years was about 110 in 1000. The chance of having a raised PSA but no cancer found on biopsy was also
about 110 in 1000.
What are the harms of treatment?
Most people in the trials diagnosed with cancer of the prostate had treatment. The commonest side
effects were erectile dysfunction (29 in 1000) and incontinence (18 in 1000).
It is very hard not to accept treatment once a cancer is found, so you need to think carefully whether or
not you want to look for one in the first place.
Further Reading and Resources:
Welch, H.G. “Overdiagnosed: Making people sick in the pursuit of health”
Dr. Michael Barry on the PSA Test: http://www.youtube.com/watch?v=zef_8-InY7U
Prosdex – online decision aid www.prosdex.com
References:
1. http://www.cancerresearchuk.org/cancer-info/cancerstats/types/prostate/incidence/
2. http://www.cancerresearchuk.org/cancer-info/cancerstats/types/prostate/mortality/
3. W.A.Sakr et. Al. “Age and Racial Distribution of Prostatic Intraepithelial Neoplasia” European
Urology 30 (1996): 138-44
4. V Moyer. “Screening for prostate cancer: U.S. Preventative Services Task Force
Recommendation Statement” Annals of Internal Medicine 157, 2 (2012) 120-135
5. T.J.Wilt & H.U.Amed “Prostate cancer screening and the management of clinically localised
disease” BMJ 346 (2013) 28-33