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 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
