Another "hard talk" Carol and I had before her diagnosis with ovarian cancer was the need to balance quality of life and quantity of life. Both chemotherapy and radiation can have profound side-effects, some immediate, but gradually dissipating, others causing permanent damage.
How much quality of life are you willing to give up to live longer?
I remember talking with my dad, over his kitchen table, as he was considering high-risk bypass surgery to correct congestive heart failure. He was no longer able to fish or garden, two of his great joys in life. He asked what I would do and I replied, "If I could no longer do the things that brought me joy, I would have the surgery." He opted for the surgery, had a stroke during the operation, and made his transition a few weeks later.
Carol and I talked about my dad and what we would do in a similar situation; we both agreed, "I would have the surgery." So even after she opted for surgery and chemotherapy to treat her ovarian cancer, she always had the option, "if this becomes too painful or the residual effects take away my quality of life, I will stop the treatments."
Discussing these difficult circumstances before the crisis arises makes your decisions and your acceptance easier when decision time comes.