Eli5 How does radiation therapy actually work? Like how doesnt it break down more of the body and make the cancer worse or something like that? And does it target only cancer area or everything?
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The more radiation that passes through a piece of tissue, the more that spot gets burned. It’s a lot like a sunburn, except that it extends into the flesh instead of stopping in the skin, and can be arbitrarily bad whereas sunburn is limited by how bright the sun is. So if you hit a cancer patient with multiple moderate-strength beams of radiation and angle the beams so they cross inside the cancer, the patient will get minor burns along the path of all the beams and more serious burns where they add together inside the cancer. The burned part of the cancer is destroyed and can’t grow back.
Radiation can cause cancer (just like sunburns can), so that might be why you expect it to make the cancer worse. But it turns out that the amount of radiation it takes to cause on average one cancer would also be enough to kill a person with burns two and a half times over if given all at once. So if you get radiation therapy to cure one cancer that you definitely have right now and give yourself a 20% risk of getting another cancer a few years in the future you’re a lot better off even with the extra cancer risk. A similar risk/benefit calculation is used for some chemotherapy drugs that might eventually cause cancer but definitely help treat the cancer the patient already has (e.g., cisplatin and nitrogen mustards).
There are some fantastic responses here already, just wanted to add something on:
We are getting much better at targeting radiotherapies to the point where they are usually trained pretty accurately on just the tumour now – the issue is thay unfortunately even when lying completely still, unconcious even, we make small movements through breathing etc.
One project researchers are currently working on is *predicting* these movements and making microscopic adjustments to the targeting to account for them. It’s pretty cooool!
Source: I work in fundraising and Cancer Research UK (largest charitable funder of Cancer Research in the world, second overall) are a client.
Imagine you’re talking down the street, and you look through the window of your neighbor’s house and you see that their kitchen stove is on fire. The fire department shows up, and is tying to come up with a plan to deal with the fire.
There’s a couple of things they can do with the tools they have
1. They can break down the front door with an axe, tear the stove out, and chop the power line to it, and throw it out. The problem here is a broken door, some other collateral damage to the kitchen like the cabinets or other appliances. And since they just tore out the stove instead of putting out the fire, maybe there was something else on fire that they didn’t notice
2. They can activate the sprinkler system. The stove fire will definitely be put out, but everywhere in the house will get wet. The longer the sprinklers are on/the longer it takes to douse the stove, the more stuff in more rooms will get waterlogged and ruined.
3. They can smash a window, and point a fire extinguisher at the stove and let loose. They’re aiming primarily at the stove, but anything in the direct line of fire in front of the stove (the window, the rug, maybe a chair, will also get at least a little gunked up. And if they miss, something else will get really gunked up and the fire won’t be out.
The Axe is surgery.
The Sprinkler is chemotherapy.
The Fire Extinguisher is radiation.
With radiotherapy, the goal is to deposit most of the energy from the beam into the cancer cells, and only the cancer cells. You don’t want to miss and ruin something else, so they take very detailed scans/images and come up with a very precise plan in advance. But hitting some stuff on the way in (for example, skin or muscle), is hard to avoid. So one way to deal with this is to take the shots from a bunch of different angles over a bunch of different low-dose sessions. That way, the only thing that gets a high cumulative dose is the cancer.
Radiation oncologist here:
Imagine having a boat in your driveway. If someone poked a bunch of holes in the boat, you could just patch the holes before taking that boat out on the water.
Now imagine you are sailing that boat as fast as you can. If someone pokes a bunch of holes in the boat, you take on water and sink before you can patch them all.
For the same reason, fast-growing cancer cells are much more easily killed by radiation compared to normal cells. They’re actively using and replicating their DNA, so when radiation damages the DNA they die.
In addition, modern radiation therapy techniques can deliver very precisely-shaped radiation fields, so that you can deliver a high dose to a tumor with much lower doses to the surrounding normal tissue.
So radiation oncology is based on selectively killing cancer cells with biology (radiation sensitivity) and also anatomy. (aiming toward tumor and away from normal tissue)
Short and simple explanation:
Cancer cells are weaker than your normal healthy cells.
So radiation and chemical therapies try to kill you to the point where cancer cells die and not your healthy ones.
It is a very thin line and hard to stop at the correct place (cancer cells dead, healthy cells barely surviving)
One point not mentioned here: normal cells, when damaged by things like radiation, pause their agenda to grow/divide and focus on repairing themselves. Cancer cells typically lack the ability to pause on growth and division, will try to divide with messed up DNA, and likely tear their genome to shreds in the process. There is a certain dosage that will kill all cells, but healthy cells respond to radiation better than cancerous cells.
1. Cancer cells are more susceptible to damage by radiation.
2. The therapy uses multiple beams, each of which isn’t really strong enough to cause much damage, but they’re all aimed at a tumor from different directions, so where the beams all meet (in the tumor) there’s a strong blast of radiation.
I’ve always thought of radiation therapy… and harmful radiation in general…as billiard balls (size depends on the type of radiation) hitting the important parts of the cell such that it can’t live anymore. I think radiation therapy is indiscriminate when it comes to cancerous or healthy cells. That’s why it’s targeted to specific areas.
That’s also why I have a very healthy respect for harmful radiation…. you’re getting ripped to shreds on a cellular level and you don’t feel it while it’s happening…I imagine.
I think Scishow explained it once as something like: Imagine radiation as a dose of poison. Hungry cells will eat some of the poison, but cancerous cells eat way more than normal cells so they eat way more of the poison. So, the cancerous mass will have eaten a lot of poison, and will hopefully die to it before your normal cells do.
the body removes damaged cells. Radiation damages good and bad cells, but bad cells get hit more.
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