Think it depends. Like a lot of other cancer stuff, there's variability. Most of the common prostate cancer is that easy and in fact they don't even treat it. My wife's grandfather was told they would basically do nothing until it started getting bad., and he died of unrelated heart failure years later without his cancer progressing.

Sounds like his was not so livable. Also unclear if he tried ivermectin instead of traditional treatment, or as an additional hail Mary. I've known people who had cancer and they tried anything and everything alongside their treatment, in case anything would help. I also knew one guy that thought just vitamin c would cure his cancer and declined any other treatment, and got killed by what may have been a supremely treatable cancer.