Other reasons apart, cancer treatments can affect men both mentally as well as physically which also impacts the man's partner. In such situations it does require tolerance and understanding by the partner. The first thing to do it to discuss it with him, if you have not already done so - you don't say and the two of you may perhaps find ways of becoming closer. Is hubby generally depressed and has he spoken with his GP about this? If this has already been tried I wonder if you both could get some professional help.