Researchers: Daily Aspirin Prevents Cancer
Friday, August 10, 2012 8:06 PM
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A new study bolsters the case that daily aspirin may help protect
against cancer, although the effect seems weaker than previously
thought.
And the final chapter on the popular but
controversial drug has yet to be written, experts say, because like
earlier research the new work has considerable limitations.
"News about the cancer potential of aspirin
use has been really encouraging lately," said Dr. Michael Thun of the
American Cancer Society, who worked on the study. "Things are moving
forward, but it is still a work in progress."
Medical guidelines in the U.S. already urge
people to take low doses of aspirin to prevent heart disease if the
predicted benefits outweigh the risk of side effects, or if they have
already suffered a heart attack.
Whether those recommendations should be broadened to include cancer prevention is still up in the air, however.
Earlier this year, an analysis of previous
clinical trials showed that people on aspirin were less likely to die of
cancer than those not on the medication, with a 37-percent drop in
cancer deaths observed from five years onwards.
The new report, published Friday in the
Journal of the National Cancer Institute, is based on real-life
observations instead of experiments. It includes a decade's worth of
data from more than 100,000 men and women in the U.S., most over 60 and
all of them non-smokers.
People who said they took daily aspirin -
whether 'baby' or adult strength - had a 16-percent lower risk of dying
from cancer than non-users overall, Thun and his colleagues found.
For men, the difference came out to 103 fewer cancer deaths a year per 100,000 people; for women, the number was 42.
The effect was strongest for
gastrointestinal cancers, such as colon cancer and stomach cancer. But
it didn't seem to matter whether people had been on aspirin for more or
less than five years.
Because the study wasn't a clinical trial,
it's hard to know if the findings can be chalked up to aspirin or if
something else is at play.
Still, Thun said the results would favor
broadening the aspirin guidelines to include cancer prevention based on
an individual risk-benefit assessment. But he added that it will take
scientists a few years to mull over all of the existing evidence.
LONG-STANDING CONTROVERSY
Other researchers are more skeptical. Dr.
Kausik Ray of St. George's University of London, who has studied
aspirin, said the new study did not look at overall death rates or side
effects such as serious stomach bleeds.
"This is not a drug without side effects, so what you have to look at is net benefit," he told Reuters Health.
Earlier this year, Ray's team published an
analysis of previous aspirin trials showing the medication did not
prevent deaths from heart disease or cancer, and was likely to cause
more harm than good.
One of the problems with the new study as
well as with previous aspirin trials, he said, is something called
detection bias. People who develop stomach bleeding from aspirin are
likely to get their bowels checked out by a doctor. As a result, doctors
may find and remove tumors or precancerous polyps, which could prolong
the patient's life - the idea behind colon cancer screening.
So far, most aspirin trials have been
designed to test the drug's effect on heart disease. Ray called for
trials that specifically check people for new cancers at given intervals
to weed out the selection bias marring the previous research.
"I don't think we have enough hard evidence suggesting everybody should be taking" aspirin, Ray said.
When it comes to cancer, the
government-backed U.S. Preventive Services Task Force agrees. It
discourages the use of aspirin to stave off colorectal cancer in people
at average risk for the disease.
Read more: Researchers: Daily Aspirin Prevents Cancer
Important: At Risk For A Heart Attack? Find Out Now.
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