The only thing that bothered me was the metaphor of the cancer being alien. It's not, which is worse: it's you. The cancer cells are your cells. Perhaps a better metaphor is that of a traitor.
I don't think people realize that cancer is just a very slightly modified you. Hitch factually knows this, I'm sure, but it's a damn hard thing to conceptualize.
I heard someone on reddit the other day say that at conception, you've selected yourself to exist, which I thought was equally as mind bending :P