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A daily
low dose of aspirin significantly reduces the number of
deaths from a whole range of common cancers, an Oxford University
study has found.
The
20% drop in all cancer deaths seen in the study
adds new evidence to the debate about whether otherwise
healthy people in their 40s and 50s should consider taking
a low dose of aspirin each day.
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Aspirin
is already known to be beneficial for those at high risk of heart
disease. But among healthy people, the benefit in lower chances
of heart problems only marginally outweighs the small risk of
stomach bleeds.
The large
size of the effect now seen in preventing cancer deaths may begin
to tip the balance in favour of taking aspirin, the scientists
suggest, but say that it is a matter for the health bodies who
write treatment guidelines.
;These results
do not mean that all adults should immediately start taking aspirin,’
cautions Professor Peter Rothwell of the Department of Clinical
Neurology at Oxford University, who led the work. ‘But they
do demonstrate major new benefits that have not previously been
factored into guideline recommendations.’
‘Previous
guidelines have rightly cautioned that in healthy middle aged
people the small risk of bleeding on aspirin partly offsets the
benefit from prevention of strokes and heart attacks, but the
reductions in deaths due to several common cancers will now alter
this balance for many people.’
These
results do not mean that all adults should immediately start
taking aspirin. But they do demonstrate major new benefits.
However, he
adds: ‘I don’t think it’s necessarily right
for the person who did the research to say what guidelines should
be. We can’t say with absolute certainty that there won’t
be some unknown harm in taking aspirin for 30 years, but it looks
as if there would be pretty large benefits in reducing cancer
deaths. People have to accept there’s some uncertainty here.’
Professor
Rothwell and colleagues recently established that a low dose of
aspirin (75 mg per day, or a quarter of the normal dose taken
for pain relief) taken for longer than five years reduces death
rates from bowel cancer by more than a third.
In this new
work, scientists from Oxford, Edinburgh, London and Japan used
data on over 670 deaths from cancer in a range of randomised trials
involving over 25,000 people. These trials compared daily use
of aspirin against no aspirin and were done originally to look
for any preventative effect against heart disease.
The results,
published in the Lancet, showed that aspirin reduced
death due to any cancer by around 20% during the trials. But the
benefits of aspirin only became apparent after taking the drug
for 5 years or more, suggesting aspirin works by slowing or preventing
the early stages of the disease so that the effect is only seen
much later.
After 5 years
of taking aspirin, the data from patients in the trials showed
that death rates were 34% less for all cancers and as much as
54% less for gastrointestinal cancers, such as oesophagus, stomach,
bowel, pancreas and liver cancers.
The researchers
also wanted to determine if the benefits from aspirin continued
over time. By using cancer registries and death records, they
were able to follow up what had happened to participants in three
of the trials.
They showed
that risk of cancer death over a period of 20 years remained 20%
lower for all solid cancers among those who had taken aspirin
(even though they would have been unlikely to have continued taking
aspirin after the trials finished), and 35% lower for gastrointestinal
cancers.
It took about
5 years to see a benefit in taking aspirin for oesophagus, pancreatic,
brain, and lung cancer; about 10 years for stomach and bowel cancer;
and about 15 years for prostate cancer. The 20-year risk of death
was reduced by about 10% for prostate cancer, 30% for lung cancer,
40% for bowel cancer and 60% for oesophagus cancer.
As the evidence
points to a delayed preventative effect against cancer, Professor
Rothwell believes that it would be those who started taking aspirin
in their late 40s or 50s – ie before people’s risk
of cancer starts increasing – and then continued for 20
to 30 years who might eventually see the most benefit.
Professor
Rothwell estimates that in terms of cost-effectiveness, taking
low-dose aspirin daily is likely to be much more cost-effective
than those interventions already used for preventing cancer, such
as screening for breast or prostate cancer.
He does note
that more research is necessary to understand more about the effect
aspirin has on cancer.
While this
study looked at how aspirin affected deaths from cancer, Professor
Rothwell and colleagues now aim to look at any protective effect
of aspirin on the incidence or progression of cancer. The researchers
also point out that more trial data are needed on breast cancer
and other cancers that particularly affect women.
Perhaps the
most important finding for the longer term is the proof of principle
that cancers can be prevented by simple compounds like aspirin,says
Professor Rothwell.
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