We should stop saying that people should fight cancer, since they can't.

There is nothing a person can do against cancer except do what they're told by the doctors.

https://www.theguardian.com/commentisfree/2019/jan/28/stop-fighting-cancer-ordinary-illness-language

Do you have a cancer? Or are you “a brave hero fighting against the demon foe”? Have you something in your body that needs removing, or are you a heroic victim in a war you may “win or lose”? A poll by Macmillan Cancer Support has found that many people with cancer are fed up with the language of war. They want to be treated like anyone else who is ill. They want to discuss their treatment with a doctor. It is as simple as that.

Anyone with experience of a cancer knows well the lugubrious looks you get. You poor thing. We are so sorry. How long have “they” given you? Be brave. Be positive. Fight back. Don’t give in and “lose”. It suggests you lacked courage and were “beaten”.

I suggest you read the rest of the article since it's pretty short.

Another relevant article: https://blogs.scientificamerican.com/observations/lets-stop-talking-about-battling-cancer/