Can Aspirin Help Prevent Cancer? - the pros and cons
Two physicians at Harvard Medical School, Drs. Michelle
Holmes and Wendy Chen, recently wrote in the New York Times about the apparent
ability of regular aspirin use to prevent death in women with breast
cancer. They called for a randomized trial of aspirin, enrolling 3000
women with stage 2 and 3 breast cancer for five years, which they estimate
would cost $10 million. They have repeatedly tried to raise these funds
through federal grants, and have been rejected. It is possible that the
publicity from their article will result in funding from the government,
private foundations or private individuals. The first randomized clinical
trial of aspirin is now going on in Britain, funded by a nonprofit group.
They are looking at 4 cancers - colorectal, breast, gastro-esophageal, &
prostate - with results expected by 2025.
Evidence so far: Many studies in the past 20
years have shown that taking aspirin is associated with the prevention of colon
cancer. A recent study helped to refine the findings - people with
high amounts of an enzyme known as 15-PDGH in their gut lining had a 50% lower
risk of colon cancer than those with a low level, if they took the
equivalent of 2 regular strength aspirins a week. A regular strength
aspirin is 325 mg, and a ‘baby’ aspirin is usually 81 mg. (2 x 325=650,
and 7 X 81=567 - close enough). The test for 15-PDGH is not yet
available. People at high risk for colon cancer - a diet low in
vegetables and whole grains, high in red meat and processed meat, inactivity,
obesity, smoking, family history of colon cancer - should talk to their doctor
about the pros and cons of low dose aspirin. (People with these habits
might also want to make some life-style changes.)
Breast cancer: a
Columbia University study published in 2004 showed that women who took aspirin
regularly (the 325 mg or 81 mg dose was not distinguished) were 20–30% less
likely to develop hormone positive breast cancer. Aspirin did not
decrease the risk of hormone negative breast cancer. The proposed mechanism is
that by a series of physiologic steps, aspirin decreases hormone biosynthesis
in the body. The researchers also discussed the anti-inflammatory
properties of aspirin, which may reduce cancer risk overall. NSAIDS such
as ibuprofen were also associated with slightly decreased cancer risk, but not
as great as aspirin. Acetaminophen (Tylenol) did not show a protective
effect. Another study, published in 2010 by the authors of the recent
NYTimes article, looked at data from The Nurses Health Study in the US.
It found that in women living at least 1 year after a breast cancer diagnosis,
aspirin use was associated with a decreased risk of distant recurrence and
breast cancer death.
A recent study from the National Cancer Institute showed
that daily aspirin use may reduce the risk of ovarian
cancer by 20%. About 20,000 women in the US will be diagnosed with
ovarian cancer in 2014, and more than 14,000 will die of this disease, which is
hard to diagnose early enough for a cure. Early symptoms are
non-specific, such as abdominal bloating, pelvic or abdominal pain, feeling
full quickly, and urinary frequency.
Many people take aspirin to prevent heart disease, especially if they
have already had a heart attack - to prevent another. Paramedics
regularly give aspirin to a heart attack patient on the way to the hospital.
Heart attacks and strokes occur when the blood supply to a part of the heart
muscle or brain is blocked by ‘plaque’, a buildup of cholesterol, fatty
substances, cellular waste products and calcium. Aspirin helps to prevent
blood clotting in the presence of plaque. The dose to take should always be
discussed with your health care provider.
There are side effects of aspirin use, which is why it
cannot be recommended to everyone to reduce the risk of cancer or heart
disease. Aspirin can be irritating to the stomach and can cause serious
bleeding in the gastrointestinal tract. It can also cause bleeding in the
brain, known as a hemorrhagic stroke.
Here’s the real message of
this column: it looks as though a simple medicine - aspirin - could be very
important in the prevention of many common cancers. However, because of
the possible side effects and dangers of aspirin, randomized studies are
greatly needed to show its efficacy and safety. Funding is needed for
this, and it will not come from pharmaceutical companies, as aspirin is such a
common and inexpensive drug. The recent publicity about this subject has
stirred great interest. Hopefully there will soon be such studies -with
answers coming more quickly than the British study due to be finished in 2025!
Sadja
Greenwood, MD,MPH back issues on this blog
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