|Originally Aired: September 7, 2006
Genetic Map of Certain Cancers Discovered; Cancer Rate Drops
|Medical researchers have created the first genetic map of colon and breast cancer, revealing that nearly 200 mutated genes that were previously unknown help tumors grow and spread. Meanwhile, breast cancer rates in the United States have started to fall.|
JEFFREY BROWN: The news is promising on two fronts. The
journal Science reports that researchers have made important discoveries about
the genetic underpinnings of cancer.
Meanwhile, an annual report indicates, the death rates from
cancer in the United States
continue to fall. And new diagnoses of some cancers, notably breast cancer, may
have leveled off.
Here to tell us more is health correspondent Susan Dentzer. Our
Health Unit is a partnership with the Robert Wood Johnson Foundation.
Susan, let's start with the genetic research here. Now, the
background to this is new awareness that cancer is, at its core, a genetic
SUSAN DENTZER: That's right, Jeff, that it starts with
changes in genes, mutations or other changes that take place. And that's the
premise behind something called the Cancer Genome Atlas, which is a large
federally funded project getting under way, under the auspices of the National
Institutes of Health, to essentially draw up a catalogue of all of the genetic
changes that can take place that can lead to cancer.
We know we have about 30,000 genes in the human body. Some
unknown, but meaningful percentage of those can mutate or undergo other
changes, which, in turn, lead to changes in cells, which, in turn, leads to
So, if we can come up with this giant catalogue, we can
really develop a very thorough understanding of what really causes cancer, at
its genetic roots, and then come up with very targeted therapies to attack
those things that are actually matched to the genetic roots of an individual
Tailoring cancer treatments
JEFFREY BROWN: All right. So, tell us about this particular
research. What did scientists do?
SUSAN DENTZER: These scientists actually showed that that
strategy underlying the Cancer Genome Atlas could work.
They took 11 different breast cancer tumors and 11 different
colon cancer tumors. These are tumors that, collectively, represent about one
of every five cancer diagnoses a year in the country. So, it's a significant
spread of cancer.
JEFFREY BROWN: That's why they chose those two cancers?
SUSAN DENTZER: That's why they chose those, yes, and those
particular subtypes of cancers in those tumors.
They looked at those. They performed a very, very high-tech
screening process, in effect, and essentially found, at the end of that
process, that there were almost 200, 189, genetic mutations, most of which were
previously unknown, that actually were contributing, if not in fact causing
So, it's almost a way of saying they came up with a little
tiny paragraph in this long catalogue that will ultimately be developed. But
they showed that, in fact, through this process, you really can come up with
And, in fact, one researcher described these as a treasure
trove, in and of themselves, with respect to these two different types of
JEFFREY BROWN: So, the way for the rest of us to think about
this, maybe, is that it's a strategy for how to develop what?
SUSAN DENTZER: It's -- in the end, it will be a strategy for
developing very sophisticated, so-called targeted therapies, that actually look
at the actual genetic changes that lead to a cancer.
What we have now to fight cancer, once we have diagnosed it,
are very blunt instruments. We have chemotherapy. We have radiation. They come
in, irrespective of what is causing your cancer genetically, and they wipe out
lots of cells, including the cancer cells.
So, they're very blunt instruments. What the future holds,
and what we see now in certain drugs, like the breast cancer drug Herceptin, is
a drug that is specifically matched to the set of genetic changes that happen
that trigger a particular subtype of cancer.
We know that there are many, many different types of breast
cancer. If we could figure out specific, targeted therapies, something that
gets in, that either switches a gene on or off, blocks a protein that a mutated
gene might contribute to the body, whatever, we will be able to come up with
things which will be much more effective, probably much less toxic to
individuals than chemotherapy or other things are.
Now, it's important to say, these things are not going to be
flying off the shelf tomorrow.
JEFFREY BROWN: Right. That was the next question.
SUSAN DENTZER: This is a long, long process.
JEFFREY BROWN: I mean, this is -- as you said, this is just
part of mapping this atlas. So, that's...
SUSAN DENTZER: Right.
JEFFREY BROWN: ... where the research continues?
SUSAN DENTZER: That's right.
And then, of course, we have a long path ahead of us, in
terms of developing these therapies, testing them for their safety, etcetera. But
what it tells you is that, over the next 20 and 30 years, the strategy for
fighting cancers is going to change remarkably, both in terms of preventing
them and getting them very early on in the process, and, in effect, treating
them very effectively.
Successes against cancer
JEFFREY BROWN: All right.
So, the second bit of news involves data from what's
happening in the last few years. Let's just look at a snapshot of right now. Generally
speaking, cancer rates are on the decline, continuing to decline, correct?
SUSAN DENTZER: Cancer death rates.
JEFFREY BROWN: OK.
SUSAN DENTZER: And, of course, that's the gold standard.
JEFFREY BROWN: Right.
SUSAN DENTZER: That really shows that progress has been made
against fighting cancer, if you have fewer people dying. And, in effect, the
JEFFREY BROWN: Death rates, as opposed to incidence?
SUSAN DENTZER: Incidence, that is to say, new diagnoses of
JEFFREY BROWN: OK.
SUSAN DENTZER: And, in fact, cancer death rates overall have
been declining since the 1990s. And the trend is being perpetuated into the
present, across the board in the major cancers that affect both men and women,
and across all races. So, that's very good news.
One of the big drivers of that, for example, is lung cancer
declining in men, because fewer and fewer men are smoking. So, those are
The other trend, though, is the one you alluded to, which is
incidence, that is to say, new diagnoses of cancers. And, across the board,
we're seeing many of those rates stabilize, or, in some cases, drop.
Now, it's not everything.
JEFFREY BROWN: Right.
SUSAN DENTZER: For women, for example, incidence of melanoma
is going up; incidence of lung cancer is going up. So, again, it's not
But the big one that people were getting quite excited about
was that new diagnoses of breast cancers seem...
JEFFREY BROWN: Right.
SUSAN DENTZER: ... to be leveling off. And that's important,
because those rates were climbing in the 1980s, and giving people a lot of
If we get more evidence in future years that those rates are
continuing to stabilize, or even decline, that will be very good news, indeed.
Meaning behind the data
JEFFREY BROWN: So, that is great news, for the moment, on
breast cancer. But you're saying that it's -- still, the jury is out on whether
how meaningful that is.
SUSAN DENTZER: Right. You really want to see several years
of data cropping up, showing the same thing.
And, also, frankly, there are other things in the
environment, we know, which could drive things the other way.
We know that rates of obesity among adult women are rising. Obesity
is correlated and linked to breast cancer rates. So, we can't pop the champagne
bottle yet. We will have to see how these trends play out over time. But, at
least for now, there's some sense that the rates -- that new diagnoses are
JEFFREY BROWN: Yes.
And is there any thinking on why that is happening?
SUSAN DENTZER: Very speculative at this point, but one of
the points of speculation, for example, is that hormone therapy use among women
dropped off sharply once, in 2002, it was reported, the major federal study
reported, that there were higher breast cancer risks attendant using hormone
A lot of women went off it at that point. It could be that
we're beginning to see some signs, in terms of the cancer diagnoses, that that
trend in fact played out.
But, again, it's speculative. And, really, it will take
several more years of data to find out what really happened.
JEFFREY BROWN: All right, Susan Dentzer, thanks again.
SUSAN DENTZER: Thanks, Jeff.