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Lung cancer staging

Health professionals use special terminology referred to as stages to concisely communicate the progression of cancer disease. Learn how cancer is classified based off the size of the tumor, the involvement of lymph nodes, and whether metastasis has occurred. Created by Amanda Grieco.

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Video transcript

Voiceover: I'm sure that you've heard people say things like "She's battling lung cancer". Or "I'm fighting lung cancer". So, why don't you and I follow this idea? Think about a strategy that you would use if you were battling an enemy in a town. I know the first thing that I would do is figure out where my enemies are hiding so I know where to go to fight them. And I'd also like to know if I'm fighting a few enemies in one place, or a few groups of enemies in several locations, because this is gonna change the way that I fight them, right? Well, this information on where and how many locations a mass of cancer cells is located is called the "stage". Well, I might use some sort of surveillance in the town to collect this information, like cameras or binoculars. I'm gonna use medical imaging instead, in the lung cancer patient, to gain the information on the cancer cells in the body that I'm looking for. The type of medical imaging that I'd use is computerized tomography scan. This is also frequently called a CT, or some people call it a CAT scan. And it's just several X-rays compiled together to generate a 3D view of the cancer cells. Or I might use an MRI, which is a magnetic resonance image. And it gives a similar image to the CT scan, but it doesn't use radiation to take the picture. And finally, maybe I'd use a PET scan, or a positron emission tomography. It also gives a 3D image, but it's based on highlighting the high metabolic activity of these rapidly dividing cancer cells. The first thing I'm gonna ask of these images is, tell me the size of the cancer or the tumor, and where in the lung, or immediately near the lung, is it located? Then I'll represent this information with a "T" for "tumor size". Makes sense right? And I'll follow it with a number one through four, where one means the tumor is less than the size of a quarter in American currency, and only in one small confined location in the lung. All the way to four, where the cancer is in multiple locations in the same lung or it's begun to spread directly nearby the lung. So, like here, in the fluid around the heart. And just like enemies in the town would use streets to get around to new locations, cancer cells will migrate into lymph vessels and spread out. Do you remember what lymph vessels are? They're vessels that pick up the immune cells and proteins that we'd find in tissues and bring them to lymph nodes located all over the body where fluid is screened for infections. In the chest, there's several lymph nodes. The mediastinal lymph nodes, here. And the Hilar lymph nodes, here. And these lymph nodes are often the first places in the lymphatic system that the cancer cells from the lungs will travel. Makes sense, because they're so close. So, it's important to know if cancer cells are in lymph nodes here, or if they're in lymph nodes even further away from the lungs. For this category of information, I'm gonna use an "N" for node, followed by a number zero to three, where zero is gonna mean that there are no cancer cells present, currently. And three would mean that cancer cells are present in lymph nodes on both sides of the chest. But cancer cells in the lymph nodes nearby the lung is very different from cancer cells that are spread to the bone or to the liver or to the brain, right? This happens in a process called metastasis. So the last category here, that I'm interested in representing with an "M", will be followed by a number, either zero or one, where zero means no metastasis has occurred and one means the cancer has spread to one or many locations outside the chest. So, this is really thorough information. And with so many combinations of numbers and letters, it might get pretty confusing. If I told you that a person's stage of cancer is "T4 N1 M0", and even though I know you understand what I'm saying now, sometimes medical professionals will group these different combinations together and simply tell a patient that they have "stage three" cancer. I'm not gonna go through the groupings because it gets messy, but I did wanna mention that TNM staging can be simplified. Okay, but there are two types of lung cancers, non-small cell and small cell. And up until this moment, I haven't indicated that there's a difference in the staging systems between the two, but actually there is. TNM staging is used mostly in non-small cell lung cancer. And there's a good reason for this. It's because non-small cell lung cancer tends to divide and spread a little bit slower than small cell lung cancer. So it's often diagnosed before it's too far advanced, meaning it hasn't spread all over. But a diagnosed small cell lung cancer tends to be in multiple locations in the body already. So, detailed information on stage isn't as important here. What's important is simply knowing. Is the cancer contained to the chest, meaning the lungs and the lymph nodes? And if it is, it's called "limited stage". But if the cancer is already spread outside the chest and in multiple locations in the body, it's called "extensive stage". In either case, the stage of the lung cancer is gonna help decide things like prognosis and plan of attack with treatment.