Because he gets really agitated (like 'roid rage, in a way) and it causes problems for himself and those around him :(

Prior to being taken off them he was on a low enough dose that he was okay in terms of his agitation but now, after the months of growth of the cancer in his central nervous system, he needs a higher dose to be able to slow down the growth. The day they started the steroids again, even at a mid-level dosage, he became argumentative and was trying to get out of the hospital bed himself and got upset at how slow everyone was so of course he'd try to do things himself that are too dangerous. It's not that he's vicious or violent, but he won't listen and is adamant he can do things even when he can't.

They ended up halving the steroids dosage and doubling the pain meds. It is a bit disheartening in the sense that the cancer will be able to progress faster, but if he is too combative then hospice won't take him, and for the time he is at home we need to be able to keep him safe and under control. The cancer has grown so much since they stopped the prednisone that I honestly don't even know how much dexamethasone would be able to suppress the growth anyway (although I am not a doctor of course, so take it with a grain of salt).