Hi Pat,
I'm sorry to hear your husband is suffering in this way. Is there a social worker at the clinic where he gets treatment. If so, I'd encourage you to contact him/her and see what they have to offer. Sometimes some brief counseling is enough to get someone through a cancer-related bout of depression like this. And if need be the social worker can do an evaluation and refer your husband to someone who can prescribe anti-depressant medication if it is thought that would be helpful. This is a fairly common occurence and there are lots of options that can help, so hopefully he will find some relief. Best to you both!