THURSDAY, Oct. 21 (HealthDay News) -- People who regularly take
a low dose of aspirin may be reducing their risk of developing
colon cancer by 24 percent, a new study finds.
Moreover, for those who take low-dose aspirin (about 75
milligrams/day) but do develop the disease, their risk of dying
from it could be cut by more than a third, the researchers
For the study's lead author, at least, the data offers strong
support for aspirin's cancer-fighting potential.
"This is proof that low-dose aspirin prevents colorectal cancer," said Dr. Peter Rothwell, a professor of neurology at John Radcliffe Hospital and the University of Oxford in the UK.
"Somewhat fortuitously, it mainly prevents those cancers that are least well-prevented by screening colonoscopy," he said.
Patients at increased risk of colorectal cancer, such as those
with a family history of previous polyps, should take low-dose
aspirin long-term, Rothwell believes.
"This additional cancer benefit of aspirin helps to tip the balance of risk and benefit in favor of healthy individuals who chose to take low-dose aspirin," he added.
The report is published in the Oct. 21 online edition of
For the study, Rothwell's team reviewed data from four
randomized trials -- evaluating the ability of aspirin to prevent
vascular disease and to determine aspirin's effect on colorectal
The four trials included more than 14,000 people who were
treated with aspirin or placebo for an average of six years. During
an average of 18 years of follow-up, 2.8 percent developed
colorectal cancer, the researchers found.
Pooling the data from all the trials, Rothwell's group
calculated that taking low-dose aspirin reduced the 20-year risk of
developing colorectal cancer by 24 percent.
In addition, for those taking aspirin who developed colorectal
cancer, the risk of dying from the condition was reduced by 35
These effects were consistent across the trials and at a dose of
aspirin of 75 milligrams a day. Higher doses of aspirin did not
appear to add any benefit, the researchers noted.
The researchers also found a reduction in the 20-year absolute
risk of any fatal colorectal cancer after five years among those
taking 75 milligrams to 300 milligrams of aspirin daily. The risk
went from about 3.5 percent among those taking a placebo to 1.5
percent for those taking aspirin, the data showed.
Seventy percent of reductions seen in colorectal cases and
deaths were due to fewer cancers in the right part of the colon
called the proximal colon, but the aspirin effect did not seem to
reduce cancer in the lower part of the colon called the distal
colon, and had only a small effect on rectal cancer, the
Most colorectal cancers develop from polyps and screening
sigmoidoscopy and colonoscopy can reduce the risk by removal of
these polyps. However screening is not 100 percent effective,
particularly for cancers in the proximal colon, they added.
Dr. Robert Benamouzig, from the Department of Gastroenterology
at Avicenne Hospital in Bobigny, France, and author of an
accompanying journal editorial, said people at normal risk for
colorectal cancer should not start taking aspirin to prevent
"But if you are at high risk then, yes, you should take low-dose aspirin," he said. "Right now, the evidence seems strong for high-risk people, but not for average-risk people."
How aspirin might work to reduce the risk of colorectal cancer
is not fully known, but it may be due to aspirin's ability to
reduce inflammation, Benamouzig said.
The downside of daily doses of aspirin is the potential risk of
gastrointestinal bleeding. So, before starting a regimen of aspirin
you should consult with your doctor, experts say.
For more information on colon cancer, visit the
U.S. National Cancer Institute.