NEW YORK -- Aspirin, one of the world's oldest and cheapest
drugs, has shown remarkable promise in treating colon cancer in people
with mutations in a gene that's thought to play a role in the disease.
Among
patients with the mutations, those who regularly took aspirin lived
longer than those who didn't, a major study found. Five years after
their cancers were diagnosed, 97% of the aspirin users were still alive
versus 74% of those not taking the drug.
Aspirin seemed to make no difference in patients who did not have the mutations.
This
sort of study can't prove that aspirin caused the better survival, and
doctors say more research must confirm the findings before aspirin can
be recommended more widely. The study wasn't designed to test aspirin;
people were taking it on their own for various reasons.
Still, the
results suggest that this simple medicine might be the cheapest
gene-targeting therapy ever found for cancer. About one-sixth of all
colon cancer patients have the mutated gene and might be helped by
aspirin. And aspirin costs just pennies a day.
"It's exciting to
think that something that's already in the medicine cabinet may really
have an important effect" beyond relieving pain and helping to prevent
heart attacks, said Dr. Andrew Chan of Massachusetts General Hospital.
He and others from Harvard Medical School led the study, which appears
in Thursday's New England Journal of Medicine.
Cancers
of the colon or rectum are a leading cause of cancer deaths worldwide.
More than 140,000 new cases and 51,000 deaths from them are expected
this year in the United States.
Several studies suggest that
aspirin may help fight cancer, especially colorectal tumors. It is often
recommended for people who have colon cancer and others at high risk of
developing it. But it's not advised for wider use, or for cancer
prevention, because it can cause serious bleeding in the stomach and
gut.
What has been lacking, doctors say, is a good way to tell
which people might benefit the most, so aspirin's risks would be
justified. Chan's study suggests a way to do that.
It involved 964
people diagnosed with various stages of colon cancer who were among
nearly 175,000 participants in two health studies based at Harvard that
began in the 1980s. Every two years, they filled out surveys on their
health habits, including aspirin use.
Most had surgery for their
cancer, and many also had chemotherapy. They gave tumor tissue samples
that could be tested for gene activity. Researchers focused on one gene,
PIK3CA, that is involved in a key pathway that fuels cancer's growth
and spread. Aspirin seems to blunt that pathway, so the scientists
looked at its use in relation to the gene.
In those whose tumors
had a mutation in that gene, regular aspirin use cut the risk of dying
of colon cancer by 82% and of dying of any cause by 46% during the study
period of about 13 years.
Only two of the 62 regular aspirin
users whose tumors had the mutated gene died within five years of their
cancer diagnosis versus 23 of 90 non-aspirin users with such a mutation.
The
results are "quite exciting," said Dr. Boris Pasche, a cancer
specialist at the University of Alabama at Birmingham who wrote an
editorial that appears with the study in the medical journal. Half a
dozen drugs are used to treat colon cancer, but only one meaningfully
extends survival in people whose cancers have not widely spread, he
said.
"Now we may have aspirin. That's why it's a big deal," Pasche said.
In the study, the dose of aspirin - baby or regular - didn't seem to matter, just whether any aspirin was regularly used.
The
test for the gene is not expensive and is simple enough that most
cancer centers should be able to do it, Chan and Pasche said.
The
National Institutes of Health and several foundations paid for the
study. One of the 17 authors consults for Bayer, a leading aspirin
maker. Pasche has been a paid speaker for two companies that make cancer
treatments and has two patent applications under review related to
cancer treatment.
Researchers warn that aspirin may not be
responsible for the improved survival seen in this study. Differences in
how the patients' cancer was treated could have played a role.
For
that reason, they say the next step should be a study where some people
with the mutated gene are given aspirin and others are not, so their
cancer outcomes can be compared more directly.
One colon cancer
patient, L. Stewart Keefe, 60, a retired interior decorator and painter
from Alton, N.H., decided several years ago to try it.
"I figured,
what have I got to lose by taking some aspirin? It just seems like it
was a simple enough thing to take," she said. "For me the bleeding risk
is a very small possible consequence" compared with the risk of cancer
coming back, she said.
Associated Press