My dad just died of cancer at 91.
He went in for his first radiation treatment and took a nose dive immediately following.
Too much for him.
I am so sorry for your loss
I'm not a doctor but I wouldn't recommend radiation and chemo past 80 unless they are very healthy, have a good immune system, a positive attitude and some excess weight. It's tough on 50 year olds. You lose weight. You can't keep food down (regardless of what they say about their expensive anti-nausea medicine). And it's very very hard mentally. I'm not 80 yet but I would forego the treatment after what I've seen from family members.