He's making a martyr out of his wife.
Im sure his wife is encouraging him to continue the run, but if I was in his shoes, I would absolutely forget the presidential run to spend as much time with my wife as possible. Sadly, she is most likely going to die and soon. To help her beat the very long odds of survival, I would want to be around her. And if she does not survive, I could know in my heart I spent as much time as I could with her before she died.
John Edwards is very very selfish man. I hope she recovers.
Define soon. It's not like she is going to drop dead tomorrow or in a couple of months. It is possible that she could be alive and well 10 years from now. The odds may not be favorable, but people beat the odds. So how, exactly do you think it would help her for him to say "hon, I'm staying home because you are going to be dead soon?"
You are being very naive if you think this decision was his alone. I am 100% sure she is encouraging him to run.