This question was recently posted on the Dogen Sangha Blog:

What advice would you give regarding zazen practice for someone facing a life-threatening illness? Accepting impermanence is easy to do when one is healthy. But when faced with the ultimate reality, our confidence deserts us and we lose faith in the words that gave us strength. (But they were just words, anyway.)
As far as questions go, it's right up there with the best of them.
I thought I'd bring it here to Treeleaf for us all to consider