My grandma survived cancer 3 times (different cancers: breast, skin and ovarian) and lived to be 97. She got radiation treatment for the skin cancer at ~85. You would be surprised how long people can live and how much they can cling to life with adequate medical support. When she got cancer the 3rd time at 95 she just got meds to slow it and deal with symptoms but didn't bother with chemo or radiation, but if she was 75 she would have 22 more years of lie.