Cancer is painful and if it's terminal--really very soon--I don't see the need to stick around. However, doctors are so often wrong, and miracles do also still occur!
I personally live with chronic pain and for myself, see no reason to continue to live. HOWEVER, along with that chronic pain comes other maladies one of which is depression, so I KNOW I am not always thinking rationally.
We all have a sexually transmitted terminal disease! It's called life.
My father was given 6 months, he made it 5 weeks. My neighbor was given 1 year and he's still alive now 7 years later.
This is not a yes-no question. People will respond to any terminal disease as they will, but they might be wrong. (With that said, if I knew when I was injured what I would go through and where I'd still be now, I would have made a different choice. Now, I'm committed to the decision.)