system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does cancer actually kill someone.

Now I totally understand how cells in your brain mutating and forming a clump and growing uncontrollably can kill someone because that's the brain, and I understand that if my lungs start getting clumps I die because I run out of air. But for bone and skin and breast cancer, it doesn't seem like there is anything amazingly crucial. 
Does cancer affect the body a lot worse than I understand or is it that non critical cancers spread to crucial organs?
gpt
Well, you sort of answered you own question. You don't technically die from cancer. You die from organ failures. Though, yes, the cancer does cause the organ failures. The way they do this is the basically hi-jiack the blood stream to feed themselves, making the healthy organs suffocate.