Question about cancer

Ok so my PCP has been ordering all these tests, just to be on the safe side, not because he suspects anything, but it got me to thinking...
I told my family that if they ever find cancer in me, I will not take the treatments. I've seen too many people live a miserable existence and lose the fight. I don't want to put my family through that and for them to have hope and then have it jerked right out of their hands. I also believe that it's God's will whether or not I live.
Is this a selfish way to feel?