I have gone with the theory - if it is anything but my brain, use all the machines / treatments (too paranoid that they'll find a cure / fix 10 seconds after I die). If my brain is damaged, just let the body go, because what was I has already left.
I dont think you have any idea of how harsh treatments can be. I went through radiations and invasive surgery to treat cancer. I am already wondering how much more I will be willing to endure and permanently loose if the cancer spread. I am scared to not even have a peaceful and descent way out if things get too tough. I am under 30.
No, I am well aware of how bad treatment can be. I am just not willing to go quietly unless it is a problem with the brain. If it is mental impairment then I am already gone.