system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If Cancer is the uncontrollable spreading of cells in your body, then what is stopping scientist from creating a drug that stops the early spreading of cancer?
gpt
How do you target "uncontrollable spreading of cells in your body" without targeting "cells in your body"?

That's the #1 question of cancer treatment.  How do you kill a part of the body gone crazy, but not kill parts of the body that haven't gone crazy?
The go-to "solution" for a while has been to find ways to target the fastest-growing cells.  But that doesn't always work, and it still has side effects.  That's why people on chemo lose their hair - because the fastest-growing cells in your body, apart from cancer of course, are your hair follicles.