Research
has shown that a regular dose of aspirin reduces the long-term risk of cancer
in those who are overweight in an international study of people with a family
history of the disease.
The
study, conducted by researchers at Newcastle University and the University of
Leeds, UK, is published in the Journal of Clinical Oncology.
They
found that being overweight more than doubles the risk of bowel cancer in
people with Lynch Syndrome, an inherited genetic disorder which affects genes
responsible for detecting and repairing damage in the DNA. Around half of these
people develop cancer, mainly in the bowel and womb.
However,
over the course of a ten year study they found this risk could be counteracted
by taking a regular dose of aspirin.
Professor
Sir John Burn, professor of Clinical Genetics at Newcastle University who led
the international research collaboration, said: "This is important for
people with Lynch Syndrome but affects the rest of us too. Lots of people
struggle with their weight and this suggests the extra cancer risk can be cancelled
by taking an aspirin.
"This
research adds to the growing body of evidence which links an increased
inflammatory process to an increased risk of cancer. Obesity increases the
inflammatory response. One explanation for our findings is that the aspirin may
be supressing that inflammation which opens up new avenues of research into the
cause of cancer."
The
randomised controlled trial is part of the CAPP 2 study involving scientists
and clinicians from over 43 centres in 16 countries which followed nearly 1,000
patients with Lynch Syndrome, in some cases for over 10 years.
937
people began either taking two aspirins (600 mg) every day for two years or a
placebo. When they were followed up ten years later, 55 had developed bowel
cancers and those who were obese were more than twice as likely to develop this
cancer -- in fact 2.75 times as likely. Following up on patients who were
taking two aspirins a day revealed that their risk was the same whether they
were obese or not.
The
trial was overseen by Newcastle Hospitals NHS Foundation Trust and funded by
the UK Medical Research Council, Cancer Research UK, the European Union and
Bayer Pharma.
Professor
John Mathers, Professor of Human Nutrition at Newcastle University who led this
part of the study said: "For those with Lynch Syndrome, we found that
every unit of BMI above what is considered healthy increased the risk of bowel
cancer by 7%. What is surprising is that even in people with a genetic
predisposition for cancer, obesity is also a driver of the disease. Indeed, the
obesity-associated risk was twice as great for people with Lynch Syndrome as
for the general population.
"The
lesson for all of us is that everyone should try to maintain a healthy weight
and for those already obese the best thing is to lose weight. However, for many
patients this can be very difficult so a simple aspirin may be able to help
this group.
Professor
Tim Bishop from the University of Leeds who led on the statistics for the study
added: "Our study suggests that the daily aspirin dose of 600 mg per day
removed the majority of the increased risk associated with higher BMI. However,
this needs to be shown in a further study to confirm the extent of the
protective power of the aspirin with respect to BMI.
However,
Professor Burn advises: "Before anyone begins to take aspirin on a regular
basis they should consult their doctor as aspirin is known to bring with it a
risk of stomach complaints including ulcers.
"But
if there is a strong family history of cancer then people may want to weigh up
the cost-benefits particularly as these days drugs which block acid production
in the stomach are available over the counter."
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. The trial will compare two aspirin a day with a range of lower doses
to see if the protection offered is the same.
Information
on the next trial can be found at http://www.capp3.org
Mechanism
The
researchers believe the study shows that aspirin is affecting an underlying
mechanism which pre-disposes someone to cancer and 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 which are predisposed to become cancerous in later
years.
One
possibility is that a little recognised effect of aspirin is to enhance programmed
cell death. This is most obvious in plants where salicylates trigger this
mechanism to help diseased plants contain the spread of infection.
"We
may be seeing a mechanism in humans whereby aspirin is encouraging genetically
damaged stem cells to undergo programmed cell death, this would have an impact
on cancer," says Sir John.
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