Hey everybody it's Rishi Agrawal.
In this video, I'm going to be talking about the 8th edition of TNM lung cancer
staging, specifically metastasis.
These are the components of the M category, location
and number of metastasis.
Unfortunately, in 55% of cases of new lung cancer, the patient
already has distant metastatic disease at the time of diagnosis.
We know from the new IASLC database
that there's similar survival between patients with intrathoracic mets
and patients with single mets
versus patients with multiple lesions.
That's why in the 8th edition of TNM Staging,
there's separate categories for intrathoracic mets,
single lesions in single organs, and multiple
lesions in one or more organ.
So let's take a look at each of these specifically.
Of course, M0 is when you don't have any metastatic disease,
M1a is intrathoracic metastases.
And these can be nodules in the contralateral lung,
pleural disease or pericardial disease.
One tip I have for you is to use the sagittal images
to determine whether or not they're studding of the pleura.
Here's an axial image showing nodules that look like they might be on the fissure,
but it's hard to tell whether they're in the lung or actually in the pleura.
If you look at the sagittal images, you could see that
there's multiple nodules that are clustered on the fissures
indicating that these are pleural metastases.
For any lung cancer patient with a pericardial effusion,
it's really important to look for nodularity of the pericardium
to determine whether there's pericardial metastases.
M1b is a single lesion in a single organ.
So this patient had a left upper lobe lung cancer
and a single lesion in their right hepatic lobe.
This refers to something called oligometastatic disease,
which just means that the patient has limited metastatic tumor burden
with only one or a few sites of metastases.
These patients with oligometastatic disease are treated
more aggressively than those who have multiple metastases.
Usually the one or two sites of metastases are treated with surgery
or other local ablative therapy like radiation.
And then finally, M1c is
when you have multiple lesions in one or more organs.
So this is a PET scan of a patient with numerous
bony metastases.
All right.
I just want to talk about metastatic disease in a few specific organs.
You should know that in a patient with lung cancer,
these are the most common sites of metastases-- bone, brain,
liver, contralateral lung, pleura and adrenal gland.
The frequency of these metastases differs by cell type.
For example, small cell really likes going to the liver.
Over here are less common sites of metastases.
But I wouldn't say that these are rare.
So kidney myocardium, pancreas, spleen,
stomach, intestines, thyroid and ovary.
These are less common sites of metastases, but you will see them from time to time.
Okay.
I want to talk about a few specific organs.
The first is the adrenal gland.
And I want to talk about adrenal adenomas.
Adrenal adenomas are really common lesions.
The first thing that you should do is measure the Hounsfield units.
If it's less than ten, that's a very good sign that this is an adrenal adenoma.
Adrenal adenomas are usually not hypermetabolic on PET.
So this adenoma had an SUV max of 2.7.
Adrenal metastases, on the other hand, are going to be more dense on CT.
So this had an Hounsfield unit of 48
and the SUV max was 12.6.
Now, a lot of times
these adrenal lesions are not as simple as what I've pictured here.
If you have an old study showing that the adrenal nodule has been there
for a long time and it hasn't grown, that's a good sign that that's an adenoma.
Now, a lot of times you don't have old studies to help you.
So if you have a positive lesion on PET
and it's indeterminate on your noncontrast CT,
then you can do a contrast
enhanced washout protocol CT
or you could do an adrenal protocol MRI.
If it's still indeterminate after those studies,
then you might have to resort to a biopsy to determine
an adrenal met from an adenoma.
Bone metastases can sometimes be subtle.
So what I recommend doing is not simply using
the bone windows to look for bone metastases.
Bone windows are good when you have erosive or very sclerotic metastases,
but when you have a metastasis that's simply replacing the normal fatty marrow,
then the soft tissue windows are usually a lot better for those metastases.
So in this case, you can see that there is a lesion in the right
femur that replaces the normal fatty marrow.
And it's really hard to see on the bone windows, but it's much easier on
the soft tissue windows.
Liver metastases can
also be difficult to see, especially if you're not using contrast.
This is a patient who had a lung cancer screening CT and you can see that there's
some mild heterogeneity of the liver parenchyma on regular soft tissue windows.
But when you narrow the windows to liver windows,
you can see those lesions a lot clearer.
Intramuscular metastases can also be challenging.
If you were going fast through this study, you might easily
miss this left paraspinal metastasis.
And that's why I recommend using the coronal images
to look at the subcutaneous soft tissues and the muscles.
You can see that this lesion stands out a lot better
on the coronal images compared to the axials.
And then finally, renal metastases.
These are not very common, but they're not rare either.
One of the reasons why renal metastases may be overlooked
is that on the PET scan, the renal collecting system
may be very bright because of excreted FDG.
So it's really important to scrutinize the CT to look for cortical lesions.
Okay, that's it for this video
on the M category of TNM staging for lung cancer.
If you have any questions about this topic, please leave me a comment below.
Thanks.