There is no Stage V. Something like pancreatic cancer or lung cancer can take one out pretty quickly if choosing not to fight it or forego chemotherapy.
HOWEVER...
One first needs to be a resident of the states where physician assisted suicide is legal to qualify for that service. Currently, these states are: Vermont, Maine, New Jersey, Colorado, Montana, Washington, Oregon, California and Hawaii.
What's really important if you are not classified as imminently terminal is to transfer residency to one of these nine states, so you have ready access to physician assisted suicide when the time comes.
Recently, a polyp was found in my gallbladder by an ultrasound. If my next ultrasound in the spring reveals a malignancy, I have contacts in both Vermont and Colorado where I could immediately transfer my residency to if I opt to forego treatment, and my very membership here should make it clear I might decide to access legal assisted suicide in Vermont or Colorado