the right to choose

This is a hypothetical situation OK.....

Let's say I am diagnosed with cancer and my finances are limited. The doctors tell me that I have 1-2 years to live and medical treatment would cost drain my finances. The end result would still be death. It's only a matter of time and the quality of life I choose before I go.

Would I have a right to refuse treatment and let the disease take its natural course ?
Would I have the right to choose not to let the surviving members of my family suffer ?
What if I become delirious or incapacitated and cannot refuse ?
Would it be legal to state it in a Power of Attorney ?

I don't see myself popping pills like its a whole meal. I realize that any illness brings with it a considerable amount of suffering but I'd like to be minimal. I don't want to cause suffering to my family members and most of all, I want to live my remaining days to the fullest !