How Aspirin May Help Prevent Certain Kinds of Cancer

Uploaded by PBSNewsHour on 21.03.2012

bjbjLULU JEFFREY BROWN: Next: A new batch of studies point to the potential benefits
of taking aspirin to treat cancer, but also raises important questions. Ray Suarez has
the story. RAY SUAREZ: The new findings were published in a series of studies in the medical
journal The Lancet. They add to other research suggesting aspirin could play a role in combating
a variety of cancers. Among the most significant findings: A daily low dose of aspirin taken
for three years reduced the risk of cancer by roughly 25 percent. And regular use of
aspirin over more than six years also reduced the chances of a cancer metastasizing. Patients
had few side effects from the aspirin. But some doctors and researchers say the case
for using aspirin as a way of preventing or treating cancer is hardly closed. Dr. Andrew
Chan wrote a commentary about these issues to accompany the studies in The Lancet. He's
an associate professor of medicine at Massachusetts General Hospital and Harvard Medical School.
And, Dr. Chan, The Lancet is pretty straightforward. The articles conclude regular use of aspirin
reduces the long-term risk of several cancers. What numbers did they crunch from already
existing aspirin studies to come to that conclusion? DR. ANDREW CHAN, Massachusetts General Hospital:
Well, what the authors did was, they looked at a series of clinical trials that were conducted
in the '80s and '90s and through the 2000s to look at the use of aspirin in the prevention
of vascular disease. And what they did was looked at cancer outcomes in those particular
trials and also linked those trials to cancer registries in the United Kingdom. And what
they found was that the individuals that were in the study that were randomized to the treatment
of aspirin did have a lower risk of dying from cancer over time. RAY SUAREZ: Now, are
we talking among the several thousand people they were watching about a few. . . DR. ANDREW
CHAN: Right. RAY SUAREZ: . . . less -- less-often-occurring cases of cancer, or are we talking about a
significant effect in that population? DR. ANDREW CHAN: No, we're seeing pretty significant
effects. I think overall they saw about a 15 percent reduction in death from any cancer
over time. So it is a substantial reduction, when you think about the fact that cancer
is one of the leading causes of death for patients. RAY SUAREZ: Was this therapy found
to be particularly effective against certain kinds of cancer? DR. ANDREW CHAN: Yeah. They
did see some particularly strong reductions in the risk of colon cancer. And also they
did see some strong reductions in the risk of other types of female reproductive cancers,
like uterine cancer and cancers of the breast. So there are various cancer types that seem
to be particularly affected. But there was a uniform benefit across all cancers. RAY
SUAREZ: Is it possible to speculate on why this happened? We know what aspirin does when
it's used to treat other maladies. What could it have been doing mechanically in the body
that also provided this effect against cancer? DR. ANDREW CHAN: Well, there's definitely
been a wealth of data that's emerged in the last couple of decades, even, that has shown
that aspirin does have very significant anti-cancer effects. There have been a range of mechanisms
proposed. I think one of the leading mechanisms that's been shown is that aspirin seems to
block key enzymes that are responsible for cancer's growth and spread. These enzymes
known, known as cyclooxygenases, produce prostaglandins. And prostaglandins are known to be cancer-promoting.
So that's one predominant mechanisms that s been hypothesized to be at play. But there
really are other mechanisms. And one of the things that we're really learning more and
more about aspirin is that aspirin has many, many different effects in the body, and it
just happens that many of these effects seem to be anti-cancer in nature. RAY SUAREZ: But
we also know about aspirin's side effects, gastrointestinal bleeding and ulcers, brain
bleeds, higher risk of stroke. How do you measure the added risk of these side effects
against the cancer suppression effects of aspirin? DR. ANDREW CHAN: Yes. I mean, that's
definitely the caveat of these studies is that aspirin is definitely not for everyone.
And we do understand that aspirin does have significant side effects, as you mentioned,
including gastrointestinal bleeding, and, more rarely, intracerebral or intracranial
bleeding or bleeding strokes. And those are definitely circumstances that can be potentially
dangerous and significant. So people do have to worry about those, particularly if they're
taking aspirin over a long period of time. So I think what we really need to move forward
on is understanding how people need to individualize their risks of these side effects in the context
of their individualized risks of developing either cancer or vascular disease. So I think
at this point in time, we're not ready to make a broad recommendation that people take
aspirin. I think, instead, we're really encouraging folks to talk to their doctors to see if aspirin
makes sense from them, in view of their particular risks of either developing cancer and heart
disease or having a side effect from treatment. RAY SUAREZ: So, let's follow up on that a
little more. What do we have to know before we, in effect, go wide with suggestion of
this as a therapy? After all, it's a very cheap drug with known side effects. Would
family history, a predisposition to cancer be something that might have a doctor recommend
it to an individual patient? DR. ANDREW CHAN: Well, it's a great question. And I think it's
something that remains to be investigated further. I think we know that there are certain
risk factors that seem to be particularly important to consider. I think, last year,
there was a very important clinical trial looking at the use of aspirin in patients
that had a hereditary form of colon cancer. And in that study, they showed over a long-term
follow-up that those patients did have a lower risk of developing colon cancer over about
a 10-year period. So, certainly, patients that have a genetic predisposition to some
problems, like, you know, colon cancer, would probably stand to benefit, and in view of
the side effects, would probably -- the benefits probably would outweigh the risks. But beyond
that, I think we're still looking at different risk factors and trying to analyze sort of
what are the most important ones to consider. A lot of that work has been done in the cardiovascular
literature. So there does appear to be certain algorithms that people can use to assess someone's
cardiovascular risk, and use that as a way to kind of stratify folks for aspirin therapy.
But that work is still relatively preliminary in the cancer field, and I think what we're
going to see in the coming years is more and more of an effort to individualize treatment
and prevention in patients for cancer, because different risk factors are at play for different
types of cancer. RAY SUAREZ: Dr. Andrew Chan, thanks for joining us. DR. ANDREW CHAN: Sure.
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