Voiceover: Before we start to talk about lung cancer,
I want to talk about the basics of the lungs.
The lungs are made up of lots of airways that branch,
and every time they branch, they get smaller and smaller
and smaller and smaller and eventually they
end in these sacs called alveoli.
They end here because at the alveoli is
where gas exchange occurs with the blood
that I am drawing in red to represent the capillaries,
where blood is flowing, but all these branch airways
need to be protected from everything else
that is in the body cavity, and so there is a lung lining
that is made up of sheets of cells
that form the boundaries of the lungs
and keep everything well contained.
Immediately around the lung lining
is this protein-rich fluid,
and this fluid is pretty important because
when you take a breath in, your lungs expand
and when you breathe out, they contract.
So, there needs to be a way to accommodate this change
in the size of your lungs and this fluid helps to do that,
but we don't want fluid just seeping into the body cavity
and so it also needs to be contained.
That means that there is another lining
on the other side of the fluid keeping it well contained.
Let's go back to the airways for a minute
because the airways are supported by lung tissue
and if we take a section of them here,
I will explain more what I mean.
So, let's draw some cells here.
These cells are very close together
and they are actually kind of glued together.
They have a special name called epithelial cells,
and they set up the borders of the airway.
So, here I'm drawing a little squiggly white line
to represent air that is going to be
flowing through this airway.
On the other side of the epithelial cells is
where the lung tissue is, so you can already see
that these cells are anchored to the tissue
and help to keep the structure of the airway.
I'm going to go come back and talk about
more of the proteins and the structures
that you would find in the lung tissue,
but for a minute, let's just focus back
on these epithelial cells.
Let's just imagine for a minute
that one of these cells becomes damaged or mutated
and starts to grow uncontrollably.
That's really important because that's one of the things
that defines cancer cells from other cells in your body.
There's just no way to stop them from dividing.
To accommodate more and more cells,
these cancer cells start to push in on the airway
and they also start to push in on the tissue underneath them
taking away space from both of these areas.
In the airway, this is a problem because
air can't flow nicely through these airways anymore.
Lung cancer patients are going to wheeze as a result of that
and they are also going to feel a decrease in lung function.
That decrease might not be so bad
if the cancer is in a smaller airway,
but if this is in one of the main airways of the lungs,
this can really be significant.
Now, the air that we breathe carries with it a lot of dust
and bacteria, and when the bacteria
gets deep into the lungs, it may be difficult
for a lung cancer patient to remove
the bacteria again past the cell mass,
and so this sets up a perfect environment
for the bacteria to settle down and cause a lung infection.
So, the body's going to mount an immune response,
and they're going to send white blood cells
to the site of infection to try to kill the bacteria
and clear the infection.
So, here's my white blood cell.
It's traveling through the blood,
and the vasculature actually becomes leaky,
allowing this white blood cell into the lung tissue
to travel up to the bacteria
so that they can actually kill the bacteria.
During this process of the white blood cell
migrating out of the blood vessel,
fluid is going to follow it into the lung tissue.
That's my yellow lines there, and the lung tissue
is going to start to swell with this fluid.
You can imagine that that means that all the lung tissue
is going to be pushed out further into the airway.
So, I'm going to draw that with dotted cells here
to show you the movement of cells into the airway.
That's going to increase all of the symptoms
that the lung cancer patient is already experiencing
with getting air in and out of these airways.
Not only is the immune system responding
to the lung infections, it is also responding
to the lung cancer cells themselves because
the immune system recognizes them as foreign.
With all this activity, lung cancer patients
will run an ongoing fever as a response from a chemical
secreted by the immune cells as they respond.
So, the immune system is really running a marathon here
and requires a lot of energy,
and unfortunately patients have trouble
keeping up with these energy demands,
and this contributes to unintentional weight loss.
But let's go back to the lung cancer cells for a minute
because these cells make a few things
that are not typical of other lung cells,
one of which is an enzyme that breaks down
tissue around the cells, and this allows
cancer cells to invade the lung tissue
and surrounding structures nearby.
If they migrate to vessels, like our blood vessel down here,
they can gain access to them
and travel throughout the body to other organs
in a process called metastasis
and form secondary cancers at these sites.
Lung cancer cells can also migrate into the lung lining,
like we had discussed in the beginning.
Let's go back to our image here.
They can migrate through the lining of the lung,
where that protein-rich fluid cradling the lungs is located,
and an immune response to cancer cells here
is going to be a lot like what we just saw.
It's going to cause swelling,
and the swelling is going to take up space from the lung
and make it even more difficult to breathe.
So now that we now the reason
for a lot of the signs and symptoms
associated with lung cancer,
you might be wondering what actually causes a cell
to become cancerous in the first place.
This is a really good question
because I kind of just brushed over the fact
that the cell becomes spontaneously mutated.
In lung cancer, there are 3 main causes of mutations,
one of which is smoking.
In fact, smoking is so strongly tied to the
development of lung cancer there is actually
a unit of measure to determine how at risk a person is,
depending on how often and how long they have smoked for.
This unit of measure is a pack year, and that means...
Let's say a patient has been smoking
about 20 cigarettes a day.
That is equivalent to a pack of cigarettes a day.
You know what, let's say this person smokes
three packs of cigarettes a day
and they have been doing this for 10 years.
So, this person would have been smoking
three packs per day times 10 years
for an equivalent of 30 pack years.
30 pack years is an important number
because it places this person at a very elevated risk
of developing lung cancer.
Another mutation source is radon,
and radon is a naturally-occurring gas
that you find in the atmosphere
that we are breathing in all the time.
To explain where it comes from, I'm going to draw
a tree rooted in some soil.
There may be a house on top of this soil,
and in this soil is a chemical that when it breaks down
it releases this colorless, odorless gas called radon
into the environment, and it can become trapped
in houses and, particularly, in basements in houses.
It builds up in high enough concentrations
that this can cause lung cancer.
Finally, a main last source of mutation in lung cancer
is medical imaging, and if a person goes to the doctor
and needs to have a picture taken
of the inside of their chest,
it might be taken with the use of radiation
in the form of an x-ray or a computed tomography scan,
which you may be more familiar with as a CAT scan,
but either way, this person is receiving a large dose
of radiation that can be harmful to their cells.
To give you an idea of the radiation dose,
if you were to take a plane ride from New York
to California, that delivers about half the radiation
that an x-ray does, and a CT scan delivers
about 100 times the radiation of a single x-ray.