If you get cancer, chances are you get treatment and die.
I've been through chemo and radiation once, if I ever am told I need to do it again, to scrape and cling to another few months of life, I'm going to laugh in their faces, put my affairs in order, go on a hell of a vacation, and Old Yeller myself.
From what I've heard about chemo, I agree with you - better to enjoy your remaining time as much as you can than to suffer through all of it.
If it happens, it'll be interesting to see how my resolve holds up as I stare into the face of mortality.
But if I get pregnant or cancer, I have no choice - I have to get treatment or die.