Firstly good luck..it’s a tough road but the medics can work wonders these days...the trick is to stay positive but I do appreciate sometimes that’s a hard ask...
I have never smoked a cigarette in my whole life and up to two days before a collapsed i was running 8km a day like 5 times a week. I do not drink alcohol either and i was actually in the best shape of my life - at least i thought!.
FWIW I was a no smoking weekend road cyclist who tried to eat properly but drank a bit on occasions when I got clobbered with colorectal cancer...By luck my radio therapy was done at a national centre of excellence and I was able to talk to one of the consultants at length about lifestyle issues. His advice was that some current research is showing that whilst life style is obviously a major factor in determining one’s risk to certain cancers the bad news was an awful lot was down to genetics and dare I say it randomness. He did however say that being vaguely fit did improve your chances of comimg through treatment, especially major surgery, successfully.