Breast cancer is the second most common cancer diagnosed in women
in the United States, right behind skin cancer.
While it largely affects women, it can also occur in men.
Fortunately, thanks to awareness, early detection, and research,
survival rates have increased
but there's still a lot we're learning.
So how far have we come
in understanding this disease?
Breast cancer affects the cells in the tissue of the breast.
It starts when these cells develop abnormally and begin to divide and accumulate rapidly
eventually forming a lump or mass.
- What happens then is that as the cells in
that tumor to continue to divide
they make additional mistakes in their DNA repair mechanisms
and DNA replication mechanisms
leading to the generation of more mutations.
More mutations generally means more variant cancer.
Hello, my name is Donald McDonnell,
I'm a professor of pharmacology and cancer biology at Duke
School of Medicine and I'm also the co-director of the women's cancer
program at Duke.
Under the breast cancer umbrella, there are three major types.
They're all different, they progress differently, and the treatments for them vary.
- There are cancers which have a protein inside them called the estrogen
receptor, and they are called estrogen receptor-positive breast cancers.
There's a second type of breast cancer which has a protein that sits on
the surface called HER2. And they're called HER2-positive breast cancers.
And then there's a population of breast cancers that neither have the estrogen
receptor, or HER2, and we call those triple-negative breast cancers.
With estrogen receptor breast cancers, a mutation in cell growth allows
the cells to respond to estrogen. Estrogens stimulate growth in a tumor
and as the tumor grows it acquires more mutations. Some risk factors for this
type involve exposure to high levels of estrogen. Those can be from your
environment, having a child later in life or even prolonged use of certain forms of birth control.
- HER2-positive breast cancers are characterized by the
fact that cancer cells of this type have a protein that sits right on the surface
and for all intents and purposes this protein then drives
processes in the cancer cell that drives proliferation and progression.
HER2-positive breast cancers are commonly treated with a drug called
Herceptin, which binds to these proteins, effectively stopping the growth and
spread of the disease.
With triple-negative, these cases occur most
frequently in younger women, particularly those of African American descent, but not exclusively.
Triple-negative breast cancers are so defined because they
don't have the proteins expressed that allows them to be defined as estrogen
receptor or HER2-positive.
And like HER2, there are some promising developments
on the horizon for triple negative.
- We are starting to see some successes in
triple-negative breast cancer with immunotherapy, and recent studies showing
that about 20% of women who are tested on immunotherapy for triple-negative breast cancer
have a positive and durable response.
So, knowing the breakdown of the most common types of breast cancer is a start
but there are also factors that can put someone at a greater risk of contracting this disease.
- So one of the common questions that I get is a researcher is what causes
breast cancer? Why do I have breast cancer? Why do none of my
relatives of breast cancer and I have got breast cancer?
And there's no real simple explanation.
Some risk factors include things such as obesity, estrogen
exposure, and genetics.
In fact, one area that has seen substantial progress is
the understanding of something called familial breast cancer
that is, breast cancer passed down from generation to generation.
In the mid-1990s, two genes
were discovered that, if mutated, actually increase your risk of breast
cancer and these are the notorious Braca 1 and Braca 2 genes.
What is interesting now is that we know quite a lot about how these Braca 1 and Braca 2 genes
influence the pathobiology of breast cancer.
We can actually take a DNA sample
and we can actually test a woman who does not have breast cancer
and ask, is she at risk for familial breast cancer?
While genetic testing is an exciting new development in the field of breast cancer diagnosis,
it's also important to stress that regular screening and early detection are big
factors in breast cancer survival rates as well.
- With the widespread use of mammography
we're now detecting all breast cancer subtypes much much earlier
than we used to.
When breast cancer is usually diagnosed
it's usually limited to one breast in one specific area in the breast,
and for the most part excision will treat this tumor followed by then what's called
adjuvant care, that is, treatments to prevent that cancer coming back again.
But if caught too late breast cancer cells can spread to other
areas of the body, including the bone, liver, and in later stages, the brain.
- From my perspective, the issues that are most important right now
are how do we block metastasis from a primary tumor?
We know that the primary tumor, in and of itself,
is not that harmful within the body
but it seeds cells that go all over the body.
One of the leading theories is that cancers can
develop what Dr. McDonnell describes as a cloak that covers the tumor allowing it
to remain undetected by the body's immune system.
- What we're focused on now is
developing drugs that can peel away this cloak and expose this tumor to the
immune system.
But then there are cases where patients suddenly go into
remission, despite the odds.
This is what Dr. McDonnell and his colleagues
are trying to make sense of
and it could all tie back to the body's immune system.
- Cancers just don't suddenly go away. Something happened within the body to
make that cancer go away. And I think most of us would agree that in large
part these spontaneous remissions are due to responses of the immune system to
that cancer.
Understanding the three main types of breast cancer, their risk
factors, and current treatment options is a first step. But fortunately daily
discoveries and innovations are helping to write a new chapter for this disease.
- Right now, I think we effectively manage and we effectively treat the disease, and
people are living longer with this disease with a very good quality of life.
I think if we are successful in harnessing the immune system and
understanding why breast tumors evade humoral immunity, that we will start
hearing the word "cure" more frequently.