Hey, everybody, this is Rishi Agarwal, and in this video, I'm going to be talking
about lung cancer screening from the perspective of a radiologist.
And this video is going to be for patients.
So if you're thinking
about lung cancer screening, whether or not it's right for you.
Hopefully this video will help you a little bit.
All right, let's start.
So this is my roadmap.
I'm going to start by talking about
how we got to the current recommendations that we have.
Then I'm going to talk about who is eligible for lung cancer screening.
What's encompassed in lung cancer screening, the risks [of screening].
And then I'm going to show you a couple of examples.
So the problem of screening for lung
cancer has been one that's been going on for a few decades, actually.
And it wasn't until the national lung screening
trial came along in the early 2000s that a widely established
method for lung cancer screening was established.
And this trial enrolled a lot of people across the country in multiple centers.
It was over fifty thousand people, and they had to be heavy smokers.
And the over 50000 people were divided into two groups.
The first group got a yearly low dose chest.
And we'll talk about what low dose chest CT is and a little bit.
And then the second group got a yearly chest X-ray.
And what this trial showed
was that the patients who got the low dose
chest CT were 20 percent less likely to die of lung cancer
than the patients who got the yearly chest x ray.
And for a radiologist, that makes intuitive sense,
because a chest x ray is a two dimensional representation of the chest,
whereas a chest CT is a three dimensional representation of a chest.
So a chest X-ray is basically one or possibly two pictures, a frontal view
and a side view, what we call a lateral view,
whereas a chest CT is multiple, usually hundreds of pictures of the lungs.
OK. And so this is a chest x ray and this is a CT of the same patient.
And what you see on the CT
is this nodule right here that I've outlined in red.
And it's really hard to see on this chest x ray, but it's right there. OK.
And so what you could see with this example is that it's much easier
to see nodules, particularly small nodules
with CT compared to X-ray.
And in 2015, the Centers for Medicare and Medicaid Services
added lung cancer screening with low dose
chest CT as a benefit for their patients.
But it didn't include all patients.
So this is the eligibility criteria as of September of 2021.
OK, these criteria will probably change in the not too distant future.
But as of right now, the age range is 55 to 77
with some private insurance covering up to age 80.
You have to be a heavy current smoker or a former smoker.
And by heavy, I mean, you have to have at least a 30 pack year history.
And to calculate your pack year history, all you have to do is take the number
of years you've smoked and multiply it by the number of packs per day.
So if you smoke one pack per day and you've smoked for 50 years,
then that means you have a 50 pack year history.
If you smoked a half pack per day for 60 years,
then that means you have a 30 pack year history. OK.
And if you're a former smoker, you have to have quit within the last 15 years.
So if you quit 16 years ago, then you're no longer eligible.
And then finally, you have to have no new respiratory symptoms.
So to explain this, let's talk about the example of breast cancer screening.
So for breast cancer screening, you go in for your yearly mammogram.
But let's say all of a sudden you feel a new lump in your breast.
Well, in that case, you wouldn't have a screening mammogram.
You would have diagnostic breast imaging.
And the difference is,
in diagnostic breast imaging, they would take specialized views
of that lump that you feel in your breast and you might even have an ultrasound.
And the same is true for lung cancer screening.
If you have new symptoms like a new cough
or you're coughing up blood or you have hoarseness in your voice,
then that might increase the suspicion that you have lung cancer.
And a low dose chest CT is not really the test for you. Instead, you
might want to get a chest CT with contrast.
OK, so that's why we say you can't have any new symptoms
because you probably should have a different test.
So what's encompassed in lung cancer screening?
Well, it's a few different things.
First is something called shared decision making.
And this is just a fancy term for a conversation that you have
with your provider about the risks and benefits of lung cancer screening.
This is an example of a shared decision making worksheet that you can find online.
But you can see that there's many different
examples of shared decision making tools out there.
And then second is smoking cessation.
And this can mean counseling with your physician or physician's
assistant or nurse practitioner, or it can mean enrollment
in a formal course with a counselor who specializes in smoking cessation.
And then third is integration into a health care team.
And what I mean by this is lung cancer screening
is not simply a test that you have and you're done.
You have to be part of
an integrated team that's able to deal with lung cancer,
if you see one, because if you just have the test
and you have no one to follow the results of the test,
then it wasn't didn't really do you any good.
So integration into a health care team of medical oncologists,
social workers, surgeons, pulmonologists
is really important in lung cancer screening.
And then finally, the actual test itself is something called a low dose chest CT.
So a low dose chest CT is a little bit
different from a regular routine chest CT that you might get.
And the reason why it's called low dose is that it's done
with much less radiation compared to a regular chest CT.
So let's talk about radiation for one second.
This is a little chart that's from a Web
comic called XKCD and it's done by somebody called Randall Munroe.
But what this shows is the amount
of radiation that you receive from multiple different things.
And I'm not going to go through all of this, but
the way we measure radiation in radiology
is usually with something called a millisievert.
And in a normal year, the average person in the United States
gets about four millisieverts of radiation. OK.
And about 85 percent of that is from natural sources.
OK, just walking around and doing your normal things in the United States.
OK, a chest CT scan is approximately seven millisieverts.
OK, so a normal yearly background is about four millisieverts.
A chest CT scan is about seven millisieverts. OK.
But a low dose chest CT is much less than that.
It's usually about one or one and a half millisievert.
So less than the amount of radiation
that you get just from living in the United States. OK.
And let me show you what a low dose chest CT looks like.
This is a low dose chest CT over here on the left.
And this is a regular chest CT or a routine chest on the right.
OK, this was done with 1.3 millisieverts of radiation.
And this was done with about 8.7 millisieverts of radiation.
And whenever I talk to patients about radiation, it's helpful
to talk about how many chest x rays worth of radiation a study was.
So this is about 13 chest x rays worth,
whereas this is about 87 chest x rays worth.
And you could see that the images are a little bit
more speckled and noisy on the low dose chest CT.
But when we look at the lungs, the lungs look almost identical.
And that's because the lungs are mostly air.
So we're able to reduce the amount of radiation.
But the image quality of the lungs remains the same
with a low dose chest as compared to a routine chest.
So there is a couple nodules right here that are just as easily
seen on this low dose chest CT as they are on the regular chest.
OK. So that's what a low dose chest means.
It's a it's a chest CT that's done with much less radiation dose.
So this brings me to something called false positives.
So a false positive is just something that we see
in the lung that we think is likely lung cancer.
But it turns out later, after additional testing that it's not lung cancer.
When we do these lung cancer screening CTs, what we're looking for is something
called a nodule, which is kind of like a little ball in the lung.
And these can be very small.
And sometimes it's difficult to tell whether a nodule is lung cancer
or something benign, meaning something that has no cancerous
material or potential.
And in fact, most of the nodules that people have are benign nodules.
So if you get a lung cancer screening CT
and we see a nodule and we call it "suspicious for lung cancer,"
then often times we'll ask you to get a follow up study in three months.
If that nodule doesn't grow in three months,
then that's a really good sign that it's a benign nodule.
Now, we might have to do additional studies
like doing a PET scan or a biopsy.
A PET scan is another radiology test in which a dye is
injected that localizes to highly metabolic tissues.
So cancers are usually highly metabolic.
So on a PET scan, a cancer will light up,
whereas a benign lesion such as a granuloma will not light up.
Sometimes a PET scan is not sufficient to tell
the difference between a benign lesion and a malignant lesion.
And so you might have to have a biopsy.
And a biopsy is just a sampling of tissue from the nodule.
So the risk of a false positive is that we see something that might be lung cancer,
you get one of those additional tests, like let's say you get a biopsy
and you get a complication from that biopsy.
And it turns out you didn't have cancer anyway.
That is the risk of a false positive.
Now, in the National Lung Screening Trial, most of the false positives
were resolved just by getting an additional follow up study.
A small minority of patients, and it's less than 1%
had a major complication from the biopsy or from surgery.
So even though false positives are a risk,
the actual risk of complications from false positives are very low.
OK, let's talk about the second risk of lung cancer
screening, and that's something called an incidental finding.
An incidental finding is just an abnormality that we see
on the study that is not related to the reason for the study.
So in this example, there is a small kidney stone in the left kidney here.
And here's an example of a patient who has coronary atherosclerosis,
which we can easily see with a low dose chest.
And here's a patient who had pneumonia.
So on the one hand, it's a good thing, right,
that we see these incidental findings because it can potentially
tell you something about yourself that you didn't know.
But the risk of incidental findings similar to the risk of false positives
is that some of these findings might lead to additional testing
that could have complications.
So let's say we found a lesion in your thyroid gland that was biopsied.
A biopsy of your thyroid gland could potentially
have a risk of bleeding or infection.
So that is the risk of an incidental finding.
It's us seeing something that could lead to potential complications down the road.
All right. So you've had the low dose chest CT.
What happens after the study?
Well, you'll get a report.
And if you've ever had a mammogram, then the lung cancer screening
report will be very similar in format to your mammography report.
And it's done through something called lung RADS.
Lung RADS is our structured
reporting system that we use for lung cancer.
So a category 1 means that we didn't see anything.
There were no lung nodules.
And you should get a screening CT in 12 months.
A category 2 is that we saw very small lung nodules, which are very common.
And the only follow up you need is another lung cancer screening in 12 months.
A Category 3 means we saw a medium size nodule.
It's probably benign, but we want you to follow up
with another chest CT in 6 months time.
A Category 4, 4A and
4B means we saw a large nodule or
we saw a nodule that grew from a previous scan.
It's suspicious.
And we want you to come for a CT
in three months or a PET/CT, or if it's even larger or more suspicious
for another reason, then we want you to come for a PET/CT or a biopsy.
Let me show you a couple examples.
So let's say you come in for your first lung cancer screening CT
and we see this small lung nodule here, which is about 4 mm in size.
We would call this a Category 2 classification
and we would ask you to come back in 12 months.
So on follow up, one year later, this lesion grew.
So now we call it a category 4B, it's suspicious for lung cancer
and we would recommend a PET/CT or biopsy.
So this brings up an important point, which is that lung cancer screening is
not a single test that you have and you're good to go for life.
It's a process that you have to have every year.
And that's because for us to tell that a cancer
is a cancer and to differentiate it from a benign lesion,
we need to have that growth in the size of the nodule.
Remember that we're trying to find lung cancers when they're very, very small,
because that gives you the best possible outcome in your treatment.
So let's take this case as an example.
If this patient didn't decide to come back a year later and waited
five years to get another lung cancer screening CT,
then this nodule would be much bigger and there would probably be
lymph nodes that we would have to deal with at that point. OK.
But because this is a small nodule, this patient has a much better chance
of survival compared to if they had waited.
So the point I'm trying to make is that it's really, really important
that you adhere to that yearly regimen of lung cancer screening,
because if you don't adhere to that yearly regimen, you're giving up on those
potential benefits of finding a cancer when it's really small.
OK, let me show you another example.
So in this example,
this nodule was about 7 mm in size.
We called it a medium sized nodule and probably benign.
And we asked that the patient follow up in six months.
And this brings me to another important point.
So on your first lung cancer screening study,
you might have to come back in three months or six months,
and that doesn't necessarily mean you have cancer.
It just means we don't have a baseline study on you
to say that the nodule that you have
has been there for a long time and we don't have to worry about it.
And then on subsequent studies, we have that baseline and we can say, oh,
yeah, that nodule has been there
for three months or six months or two years, and it's benign.
All right, so let's summarize everything that we talked about.
The first is that the NLST was a huge screening trial
and it showed that screening for lung cancer with low dose
chest CT is one of the best cancer screening tools that we have.
The second is that not all patients are eligible.
You have to be between the ages of 55 to 77
with some private insurance going up to age 80.
You have to have a 30 pack year history.
And if you're a former smoker, you have to have quit within the last 15 years
and you have to be asymptomatic, meaning no new symptoms.
This eligibility criteria will likely change in the near future
with the age coming down and the pack year history coming down.
OK, but as of right now, this is the eligibility criteria.
It's important to follow up yearly.
That's the only way we can tell whether a nodule grows or doesn't grow
and therefore is likely to be cancer or not likely to be cancer.
OK, so coming back yearly is so important for lung cancer screening.
The amount of radiation
in a low dose chest is only about 15 chest x rays and no contrast is needed.
So you don't have to have a needle prick for this test.
False positives and incidental findings
are the main risks of lung cancer screening.
But most of the time, all that is needed
is just a follow up imaging study.
And then finally, quitting smoking is probably the most important thing
that you can do to improve your health if you haven't quit already.
And I'll link below to some resources online
that will help you quit if you are having trouble.
OK, so I hope you've learned something from this video.
If you have any questions, please leave them in the comments below. Thanks.