I don't want to minimize the serious situation in which John McCain finds himself. I've had people close to me die of cancer, and I know what that is like. But I will tell you what I am thinking about this: John McCain is a man who married a woman worth hundreds of millions of dollars (after dumping his first wife,) and who consequently has not a shred of worry about how to pay for his own care, nor does he have to make decisions about paying for his own treatment at the price of leaving his family destitute.
Please, John, take a little bit of time to put yourself outside of your own privileged situation, and think about all of the people in this country who have to face what you are facing, without a huge stash of money to pay for it. Go back to the Senate and demand that this abomination be eliminated. We now know, from the behavior of your fellow Republicans, that there is no way to guarantee this except by a single payer system, minimally just extending Medicare to everyone. Spend what time you have left using your power to get that done, and you will go down in history alongside Franklin Delano Roosevelt, not Trump and McConnell and the other members of your party who will promote any evil if it benefits their backers.
Do the right thing, and die proud, John. Think about it.