system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is cancer so deadly but a person feels fine one day then the next they are told they have 4 months to live?
gpt
Exponential growth. At first cancer is a single malformed cell dividing without restrictions. That 1 turns into 2, 2 becomes 4, 4 becomes 8, 8 turns into 16, etc. With each division the number of cancerous cells doubles. (More or less)

So for the first few months or so the cancer is only a minor disruption, but soon it rapidly becomes larger and larger and starts affecting the function of the entire organ and body. Taking up nutrients and putting stress on other organs causing cascading organ failures if left untreated.