Taking aspirin long-term halves risk of hereditary cancers
28 October 2011
A decade-long study in 16 countries has found that taking
600mg aspirin every day for over five years halves the risk of getting hereditary cancers.
Hereditary cancers are those that develop as a result of a gene
fault inherited from a parent. Bowel and womb cancers are the most
common forms of hereditary cancers.
The study, which is published in The Lancet , involved scientists and clinicians
from 43 centres in 16 countries. The trial was overseen by Newcastle
Hospitals NHS Foundation Trust. It followed nearly 1,000 patients with Lynch syndrome, in some
cases for over 10 years. Lynch syndrome is an inherited genetic disorder that causes
cancer by affecting genes responsible for detecting and repairing
damage in the DNA. Around 50% of those with Lynch syndrome
develop cancer, mainly in the bowel and womb.
Evidence of the benefits of aspirin has been accumulating for
over 20 years but these are the first results from a randomised
controlled trial assessing the effect of aspirin on cancer.
Between 1999 and 2005 a total 861 people began either taking two
aspirins (600 mg) every day for two years or a placebo. At the end
of the treatment stage in 2007 there was no difference between those
who had taken aspirin and those who had not.
However, the study team anticipated a longer-term effect and
designed the study for continued follow-up. By 2010 there had been
19 new colorectal cancers among those who had received aspirin and
34 among those on placebo. The incidence of cancer among the group
who had taken aspirin had halved —and the effect began to be seen
five years after patients starting taking the aspirin.
A further analysis focused on the patients who took aspirin for
at least two years and here the effects of aspirin were even more
pronounced: a 63% reduced incidence of colorectal cancer was
observed with 23 bowel cancers in the placebo group but only 10 in
the aspirin group.
Looking at all cancers related to Lynch syndrome, including
cancer of the endometrium or womb, almost 30% of the patients taking
the placebo had developed a cancer compared to around 15% of those
taking the aspirin.
Those who had taken aspirin still developed the same number of
polyps, which are thought to be precursors of cancer, as those who
did not take aspirin but they did not go on to develop cancer.
It suggests that aspirin could possibly be causing these cells to
destruct before they turn cancerous.
Over 1,000 people were diagnosed with bowel cancer in Northern
Ireland last year; 400 of these died from the disease. Ten per cent
of bowel cancer cases are hereditary and by taking aspirin regularly
the number of those dying from the hereditary form of the disease
could be halved.
The researchers believe the study shows that aspirin is affecting
an underlying mechanism which predisposes someone to cancer and that
further study is needed in this area. Since the benefits are
occurring before the very early stages of developing a tumour —
known as the adenoma carcinoma sequence — the effect must be
changing the cells that are predisposed to become cancerous in
One possibility is that a little recognised effect of aspirin is
to enhance programmed cell death. This is most obvious in plants,
which release salicylic acid when under stress such as from drought,
or under attack from fungus or insects. It helps diseased plants
contain the spread of infection. Aspirin was first isolated from
willow bark in 1829, but the medicinal use of willow bark to treat
headaches, pain and fevers was recorded by Hippocrates (460-377 BC).
Professor Patrick Morrison from Queen’s University in Belfast,
who led the Northern Ireland part of the study, said: “The results
of this study, which has been ongoing for over a decade, proves that
the regular intake of aspirin over a prolonged period halves the
risk of developing hereditary cancers. The effects of aspirin in the
first five years of the study were not clear but in those who took
aspirin for between five and ten years the results were very clear.”
“This is a huge breakthrough in terms of cancer prevention. For those who have a history of hereditary cancers in their family,
like bowel and womb cancers, this will be welcome news.
"Not only does it show we can reduce cancer rates and ultimately
deaths, it opens up other avenues for further cancer prevention
research. We aim now to go forward with another trial to
assess the most effective dosage of aspirin for hereditary cancer
prevention and to look at the use of aspirin in the general
population as a way of reducing the risk of bowel cancer.
“For anyone considering taking aspirin I would recommend
discussing this with your GP first as aspirin is known to bring with
it a risk of stomach complaints, including ulcers.”
The international team are now preparing a large-scale follow-up
trial and want to recruit 3,000 people across the world to test the
effect of different doses of aspirin. To take part in the next trial
people can sign up at www.capp3.org
1. Burn J et al. Long-term effect of aspirin on cancer risk
in carriers of hereditary colorectal cancer: an analysis from the
CAPP2 randomised controlled trial. The Lancet, Early Online
Publication, 28 October 2011. doi:10.1016/S0140-6736(11)61049-0.
A summary and full list of authors and institutions involved is
2. Over the course of the clinical trial, funding came from
Cancer Research UK, UK Medical Research Council, European Union,
Bayer Corporation, National Starch and Chemical Company, The
Newcastle Upon Tyne Hospitals NHS Foundation Trust and Bayer Pharma.
Further international funding was provided by: Newcastle Hospital
Trustees, Cancer Council of Victoria Australia, THRIPP South Africa,
The Finnish Cancer Foundation, and SIAK Switzerland.