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?
In: 630
Radiation causes damage to DNA, particularly the DNA of a cell that is actively dividing (since the DNA strand “unzips” into two separate strands as it’s being copied).
This can cause cancer because it can damage the parts of DNA that are responsible for repairing and regulating the whole DNA strand. (Imagine a computer with a bunch of information, including a section on how to recover lost data.) That’s why radiation is dangerous in the first place.
However, cancer cells have two traits that make them especially vulnerable to this effect:
* They multiply much more often than normal cells, which means they’re duplicating their DNA much more often.
* They almost always have already lost the ability to repair their DNA effectively (because that’s how they became cancerous in the first place).
As a result, radiation therapy damages cancer cells much more than it damages normal cells. The hope is that it damages the cancer cells to the point of death before it triggers a new cancerous mutation in healthy cells. It usually does, but not always, and secondary cancers do happen sometimes (but, well, you already had cancer in the first place).
EDIT: As others note, radiation therapy is also targeted – the goal is to expose the cancer to it and not healthy cells. But that targeting isn’t perfect, and it does expose healthy cells to some extent too.
Eli5: a mosquito lands on your nose. Your friend hits you in the face with a plank. Your nose really hurts, but the mosquito is all kablooey.
The cancer is the mosquito. The plank is invisible radiation. And if you are in the US then your friend takes your house.
So I actually just read a study of the Therac-25 situation (google it, software bug caused radiotherapy machine to give people harmful/lethal doses.
But… along with that I got some education on nuclear medicine.
So “radiation” is essentially pieces of an atoms nucleus that go flying off from the atom at very high energies/speeds. There’s also gamma radiation which is energy, but that’s mostly not in play here… those little pieces of nucleus, mostly I believe protons in regard to radio therapy, crash into molecules in your body (dna, for example), disrupt their structure and cause damage. This kills normal cells and cancer cells alike.
So, just focusing on the proton for brevity’s sake.. a proton at a certain energy level will have a certain amount of penetration. This means they know how much energy they’re putting into the machine, so they can position you and/or the machine in such a way that they’ll know where the protons (radiation) is likely to stop, where it’ll end up.
It turns out that in particle physics, while a particle will lose some energy along its whole path, it will deposit the vast majority of its energy at its stopping point. Which is super interesting, I never knew that.
So, knowing how much the proton beam will penetrate, they can set things up to control where the beam will end up… and while it’ll have some effect on the cells in the path, it’ll mostly just be dumping it’s energy into where they want it. Which (hopefully) will destroy the cells there and have minimal impact on anything else!
So are tumors specifically targeted or is it a literal radiation shower for the whole body?
There are a lot of different kinds of radiations therapies. Depending which cancer and where decides which to use. You have for surface cancers a linear accelerators which accelerate an electron or photon to damage the cancer cells. Alternative radioactive source are used to be inserted into the body near/in the cancer spots to radiate the cancer very locally. The sources are tiny and are not able to radiate deep into the tissue. But as you questioned also healthy tissue will be damaged. But healthy tissue can regrow and repair (if damage is not to extensive).
Radiation damages everything. Cancer cells can’t heal themselves and die, healthy tissue can repair and does. We put alot of effort in to minimalising the healthy tissue that gets irradiated. My place does sub millimeter accuracy in its treatments.
The problem with Cancerous cells is that they’re very much still alive, and they look a lot like regular cells so they’re not being destroyed by your body.
For all its clever evolution, the human immune system isn’t that smart. If it claims to be a friend, the immune system does nothing to fight it.
We can look at cells and critically say “Yup, that’s broken and needs destroying” even if they’re still technically alive.
So most cancer therapies are based on either spotting one of the subtle traits of cancerous cells and using that to target a treatment, or simply nuking the site from orbit with targeted radiation-beams.
The challenge isn’t killing the cancer, it’s making sure the cure isn’t killing anything it shouldn’t.
So yes, Radiation therapy definitely runs the risk of causing more damage. The idea is to focus your attention on just the cancerous cells and anything nearby that *might* be cancer to prevent it from coming back.
What’s worth mentioning is that the generation of cancerous cells is actually pretty rare. If you shoot someone with a narrow-focus radiation-beam it won’t hit many cells, and the odds of those cells becoming cancerous rather than just dying outright is pretty slim.
Usually if you break something about a cell, it just dies. Cancer happens when the cell is damaged but not killed, and then passes on the damage to its descendants, or simply loses its “off switch” and just keeps reproducing forever. There’s lots of kinds of cancer.
So in principle, the treatments run a small scope of generating more cancer, but in practice if you just keep at it with multiple treatments eventually the dice will fall in your favour and all of it will be gone.
An ELI5 answer:
Radiation and chemo damage cells, particularly as the split and multiply. Cancer cells multiply more frequently than most other cell types in your body, so they get hit the most, but there is still some collateral damage. This is also why nausea/vomiting and hair loss are common side effects – your stomach lining and hair follicles replicate faster than most of the rest of your body, so they take increased damage.
My wife had Radiation after Chemo for tripple neg breast cancer. Their main concern was the damage it could cause her heart because of where the cancer was.
there is also a longer conversation about what cancer actually is.
TLDR chemo and radiation damage everything around.
A very simple analogy is sunlight with a magnifying glass. When diffuse it will apply uniformly across the region, when targeted it can become very hot. Most radiation therapy is targeted to cancerous cells with minimal impact to nearby tissue. This is either done by applying low energy radiation directly to a cancerous location internally so all energy is absorbed by the cancerous tissue, or by using multiple angles from an external beam that minimally impacts surrounding tissue, but multiplies in a single area after multiple exposures.
Latest Answers