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Lung cancer diagnosis

How do we know a patient has lung cancer? Learn how health professionals use x-rays, computed tomography (CT scans), positron emission tomography (PET scans), and blood results to confirm lung cancer in patients. Created by Amanda Grieco.

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Video transcript

Voiceover: Every person and every case of lung cancer is different, and so the course to diagnosis is often individual as well. You may know this from personal experience, and I certainly do, because my grandma's course to diagnosis was very atypical. But to at least start a discussion about diagnosis you might stick to a fairly standard course. Since it's estimated that about 90 percent of all lung cancers arise from smoking, let's give our patient, we'll name her Ollie, a cigarette. Let's say that over the years she developed a smoker's cough, but decided to see a doctor one day when she was feeling like the cough was increasing, and at times she was coughing up bloody mucus and she's consistently running a fever. Her physician would probably immediately order a chest x-ray to get a picture of what's going on inside of her lungs. Here's my drawing of what a chest x-ray film might look like. Let's say here in the lung is a round, suspicious-looking, dense mass. It would almost look like she breathed in a coin. Now a coin appearance on a chest x-ray can actually be a type of pneumonia, so pneumonia. The radiologist might wonder if that's exactly what's going on with Ollie, considering smokers are prone to lung infections, right? But pneumonia will clear or at least it will begin to clear in a few weeks with rest and antibiotics. Here are Ollie's antibiotics, and she takes them, and in a few weeks comes back for another x-ray and the radiologist finds that the coin mass is maybe a little bit bigger, maybe about the same size, but either way it hasn't gotten smaller so Ollie probably doesn't have pneumonia. So I'm erasing that here. But be careful, because this doesn't automatically mean that Ollie has cancer, and a few other tests need to be done to rule out that this just might be an outgrowth of normal, healthy cells. One of these tests is a computed tomography scan, or a CT. Let's say Ollie goes and gets one to get higher resolution x-ray images to compile into a 3D image, making it easier to determine the size of the mass in her lungs. She might also go for a PET scan. PET scan stands for positron emission tomography scan, and it's used to determine if the cells are using a large amount of glucose. Since we know that cancer cells divide rapidly, they have a high demand for energy, and that means that they're going to use a lot of glucose and will appear very bright in scans compared to background tissue in normal cells. And if the mass is a larger size or growing in size when compared to additional future CT scans, and if it appears bright in a PET scan, it's worth taking the next step, which is more invasive but it's the only way to definitively diagnose cancer, by getting a sample of cells from the mass. Let's leave the medical images behind and discuss the procedures here on the drawing of the left lung. I should start by saying that sometimes an invasive procedure can be avoided. For example, if cancer cells are found in the bloody mucus that Ollie is coughing up. But this doesn't frequently happen and so there are a few options for physically going in and removing the cells. Which option is used often is decided by the location of the cancer cells. What I mean by this is, see this blue here around the lungs? What I'm trying to show here is the pleural space around the lungs that is filled with a protein-rich fluid that cradles the lungs, and sometimes cancer cells spread to this space. That's called pleural effusion, and it causes this inflammation leading to an increase in the volume of the fluid. If this happens it will be visible on Ollie's x-ray because where lung tissue used to be it's now being covered by this fluid. An oncologist may decide to pass a needle from the outside of the body into this space and take a sample of the fluid, including the cancer cells which will be floating around in it. But let's say Ollie doesn't have pleural effusion. The medical imaging shows that the mass growing in her lung is closest to the outside of her body, like if they were here. Well then the oncologist may decide that it makes sense to pass a needle from the outside of the body, through the pleural space and into the lung itself, where a biopsy of the tissue can be taken along with cells from the mass. For this next option let's erase this mucus, and let's say that the mass is growing in one of Ollie's major airways, like right here. It might be easiest then for the oncologist to insert a tube down the back of Ollie's throat in a procedure called a bronchoscopy. This allows for viewing of her lung internally, and an attachment on the tube can be used to take a biopsy of the lung tissue and the cells. But any way that the cells are obtained, they're going to be sent back to the lab and determined if they're cancerous. This is done by looking at them and looking for hallmark signs of cancer, like specific mutations in their DNA. Early discovery and diagnosis has a dramatic impact on lung cancer prognosis, and so the sooner the diagnosis is made, the better.