I lost a friend who died from complications caused by chemotherapy. That's a true statement. It's also true that she would most likely have died at least a decade earlier, maybe two decades, had she not done chemotherapy. (She was on her 3rd or 4th relapse.)

I don't mind the above wording at all, because there's another thing that happens: people seem to have this impression that if you get cancer, follow the recommended treatment, and are in remission... that you're "done", and you "won". It isn't like that. First, the treatments have serious side effects, both short and long term. Second, cancer is never gone from your life, even if it never comes back. That doesn't mean you should not do the recommended and available treatments. Your odds of survival are almost always much much higher if you do, and imo is the right thing to do for the vast majority of people. But go into it with your eyes open. You're past the point where you get to have a conventional happy ending. You'll need to figure out how to be ok with the ending that you can still have. (Which may be a happy one! But not in the way that you imagined when you were younger.)