New research suggests that the reason aspirin may protect against
certain cancers is its ability to inhibit prostaglandins, chemicals
naturally produced by the body that are suspected of playing a
role in colorectal and lung cancer.
Prostaglandins are chemical messengers that send signals in the
body, stimulating various activities, including blood clotting
and neurotransmission. Prostaglandins are also immune suppressors,
and their inhibition might improve the body's ability to fight
Scientists were led to study aspirin because anecdotal evidence
has suggested that adults who take the drug on a regular basis
for other maladies are less likely to die of colorectal cancer.
Now, preliminary research by Mack T. Ruffin IV, MD, of the University
of Michigan Medical School, Ann Arbor, suggests that as little
as 80 mg of acetylsalicylic acid (ASA), the dosage of a baby aspirin
tablet, taken each day can lead to significant prostaglandin suppression.
By comparison, a person with a headache might take two adult-strength
tablets of approximately 325 mg ASA per tablet, as many as six
times a day.
Speaking at the annual meeting of the American Association for
Cancer Research (AACR), Dr. Ruffin described his study of 65 healthy
adults given 14 days of a single daily dose of ASA or a placebo.
The doses of ASA were 40, 80, 160, or 640 mg. Rectal tissue biopsies
were taken to monitor changes in prostaglandin levels.
Dr. Ruffin said that 80 mg/day was the lowest effective dose and
that prostaglandin production remained suppressed up to 3 days
after the last dose. In addition, the research team observed that
women produce significantly less prostaglandin than men. "Women
also have a lower incidence of colorectal cancer," Dr. Ruffin
said, suggesting a possible link.
Aspirin and Lung Cancer
In his AACR presentation, André Castonguay, PhD, of Laval
University, Quebec City, Canada, reported on a study of the ability
of various nonsteroidal anti-inflammatory drugs (NSAIDs) to suppress
the development of lung cancer in mice given NNK, a powerful carcinogen
found in cigarette smoke.
He found that mice who received unprocessed, nonformulated ASA
had 60% fewer lung tumors, compared with the control group. In
mice fed the aspirin form of ASA, tumors were reduced by 63%.
Sulindac, an NSAID arthritis medication, suppressed tumor growth
by 52%, he said, and buffered aspirin did not demonstrate any
significant protection from tumors.
Avoid 'Cavalier' Use
Even though ASA is available over-the-counter, Dr. Ruffin warned
that it should not be used in a cavalier manner, and should be
considered an experimental cancer drug. ASA has many potential
side effects, including stomach pain, bleeding ulcers, nausea,
diarrhea, and vomiting.
As many as 4% of the population cannot tolerate normal doses of
ASA because of side effects. In addition, some people are allergic
to ASA, and the drug may interfere with other medications.
"It is ironic that in this era of high-tech medicine, researchers
are taking a second look at this old standby," Dr. Ruffin
said. "Scientists are rediscovering it, and may find that
it has a potential impact beyond even what we speculate now."
Dr. Ruffin also stressed that ASA should not be used as a "magic
bullet" to prevent cancer instead of following a healthy
diet and lifestyle. Colorectal cancer is believed to be related
to the high-fat, low-fiber North American diet, and he also suspects
that there may be a relationship between prostaglandin levels