Aspirin could dramatically cut cancer risk, according to biggest study yet
An aspirin
a day could dramatically cut people's chances of getting and dying from common
cancers, according to the most detailed review yet of the cheap drug's ability
to stem disease. More than 130,000 deaths
(in the UK) would be avoided over a 20-year period if Britain's 50- to 64-year-olds took a
daily aspirin for 10 years, because the beneficial effects continue even when
the aspirin is stopped, the authors say.
A research team led by
Professor Jack Cuzick, head of the centre for cancer prevention at Queen Mary University
of London, concluded that people between 50 and 65 should consider
regularly taking the 75mg low-dosage tablets.
Cuzick said that taking
aspirin "looks to be the most important thing we can do to reduce cancer
after stopping smoking and reducing obesity, and will probably be much easier
to implement". In a briefing to journalists,
the scientist added that he had been dosing himself for the last four years,
keeping the tablets beside his bed. "I take aspirin as part of a bedtime
ritual every day and I can achieve that quite easily," he said.
However, to obtain the
newfound benefits of the drug, people would have to take aspirin for at least
five years and probably 10, the review said. Aspirin was originally
developed as a painkiller and treatment for fever and inflammation, but more
than a century after it was first synthesised from willow bark, researchers
have found more medical uses for it.
It has been demonstrated to
reduce the risks of heart attacks and strokes as well as the chances of some
cancers. But the big question has been whether the benefits outweigh the harms,
because aspirin can cause stomach bleeds, which could be potentially fatal in
some people.
Concluding that the benefits
outweighed the risks, Cuzick's team, writing in the cancer journal Annals of Oncology, said
that by taking low-dose aspirin every day for 10 years, bowel cancer cases
could be cut by about 35% and deaths by 40%. Aspirin could reduce rates of
oesophageal and stomach cancers by 30% and deaths from them by 35% to 50%.
However, taking aspirin every
day for 10 years increases the risk of stomach bleeds among 60-year-olds from
2.2% to 3.6%. In about 5% of those who have a stomach bleed, it could be fatal. Cuzick added that there was
evidence that this side-effect could be more common in people who have the
bacterium Helicobacter pylori in their stomach, which also causes peptic
ulcers. He said people considering embarking on a regime of daily aspirin
should talk to their GP and it might be possible to be tested first.
A second risk is stroke.
Aspirin is already given to some people to reduce their risk of heart attacks
or ischemic stroke, caused by blood clots, which it does by thinning the blood.
But it is likely to worsen a haemorrhagic stroke, caused by bleeding in the
brain.
The study also shows that 10
years of aspirin reduces heart attacks by 18% and deaths by 5%, but although it
reduces stroke numbers by 5%, there is a 21% increase in deaths.
All the cancers in which
aspirin has a beneficial effect have some lifestyle causes – from smoking in lung
cancer to alcohol in oesophageal cancer and obesity in all of them.
Taking aspirin, said Cuzick, "should not be seen as a reason for not
improving your lifestyle". The drug, however, would reduce the cancer risk
even in people who have a healthy lifestyle, he said.
Increasing numbers of people
in middle age are already being prescribed cholesterol-lowering statins to
reduce their risk of heart attacks and strokes. Recently there has been an
outcry over the "medicalisation" of the population and concern about
side-effects – which trial data suggest are less common and less serious than
those in aspirin. Cuzick said there was no evidence of any interaction between
the two drugs. "In many people, taking both of them is probably a good
idea," he said.
However, Cancer
Research UK (CRUK)warned that people should speak to their GP before
starting on daily aspirin. The charity said it would like to see more research
on who should and should not be taking it.
"Aspirin is showing
promise in preventing certain types of cancer, but it's vital that we balance
this with the complications it can cause – such as bleeding, stomach ulcers, or
even strokes in some people," said Dr Julie Sharp, head of health
information at CRUK.
"Before aspirin can be
recommended for cancer prevention some important questions need to be answered,
including what is the best dose and how long people should take it for. And
tests need to be developed to predict who is likely to have side-effects. "Given the continued
uncertainty over who should take aspirin, Cancer Research UK is funding a
number of trials and research projects to make the picture clearer," she
said.
Aspirin also has a smaller
preventive effect on other major cancers, according to the research paper. It
could reduce the number of lung cancers by 5% and deaths by 15%. It could cut
prostate cancers by 10% and deaths by 15%, and breast cancers by 10%, with a
reduction in deaths of 5%. There would be an overall 9%
reduction in the number of cancers, strokes and heart attacks suffered by men
and a fall of 7% in women.
Cuzick acknowledged that
people generally did not like taking pills for a long period, although, he
said, some were "more than happy to take multivitamins for many, many
years without any clear evidence of benefit. It is a regular habit."
As a generic drug – Bayer's
patent ran out in the 1930s – there are no profits to be made by big
pharmaceutical companies from the estimated 100bn tablets taken around the
world every year.
The science – and the warnings
What does the study find?
The risk of both developing
and dying from digestive-tract cancers – those of the bowel, stomach and
oesophagus – was reduced by about a third in people who took low doses of
aspirin daily for 10 years. Cases of breast, prostate and lung cancer were
reduced by about 10%, though no effect was seen on other cancers.
What do scientists recommend?
For
aspirin's anti-cancer benefits to kick in, people needed to have taken aspirin
for at least five years from the ages of 50 to 64. Most of the research was
based on low 75mg doses. The longer the drug was taken, the better its
preventive effects, until the age of 65, after which there was an increased
risk of internal bleeding. The study found no benefit in taking aspirin before
the age of 50. Scientists recommend that people consult their GP before taking
daily aspirin to prevent cancer.
How does aspirin prevent
cancer?
There are two theories.
First, inflammation in the body causes cells to divide, which increases the
risk of them mutating into cancerous forms.
Because aspirin reduces
inflammation, it lowers the risk of cancerous cells developing.
Second, cancer cells can
piggyback on blood platelets, which help the blood to clot. Aspirin thins the
blood by making platelets less sticky, which may also make it harder for them
to carry cancer cells and so spread the disease.
What are the risks?
Aspirin can cause bleeding in
the stomach and bowel. This can be serious, especially in the over 70s, but
rarely affects younger people unless they have an underlying condition.
"My personal advice
would be that everyone 50 to 64 should consider taking aspirin. You should talk
to your GP first to see if you've got any of the major risk factors for
bleeding, but if not I think the benefits substantially outweigh the
risks," said the senior author, Prof Jack Cuzick.
Nishad Karim
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