What I can guess is the fact that he must be under a serious stage of his treatment chemo/artificial coma, something like that.
I know a lot of people that had to endure cancer treatments (including my mother), and some of the stages are really hard for your body. Hope he will survive.
Sadly, with all the poison they put in our food/furniture/houses, air and water, the number of cancers is gonna skyrocket in the next years, and it's probable than many of us will have to suffer from it.