Very little eating and drinking, how long can this last?

My husband has just been diagnosed with stage four lung cancer. It has spread to his brain and shoulder and some of his bones. He has so much depression over his diagnosis after being a very proactive health person and has given up and is refusing to eat or hydrate. He has lost over 60 pounds. How long can this lack of eating and drinking during the day go on before he has an Organ shut down? Does anyone have a similar situation? He is 6’2”and 146 pounds he is doing immunotherapy treatment but they told him that they would stop it if he did not try on his end because the therapy treatment would not be as effective. I take care of him 24 hours a day at home and have no problem doing that, but I am basically sitting on the other couch watching him waste away to skin and bones. It’s heartbreaking I would have thought after 32 years of marriage he would have fought a little harder to stay with me. I guess no one can tell what they would do unless they are in that situation so I am not judging him, it is just very difficult to work so hard on my end and not get the results on his end. My mother who is 87 also helps me, she is in good health and my sister who’s 62 is a lifesaver because I could not shower him without her. He requires two people to hold him up because he has so many things at one time you would not believe it. He has a neuroma in his ear which was treated, he had his brain and his shoulder radiated, they found he had a metastasized tumor in his shoulder after complaining about shoulder pain for a year that the doctors did not diagnose until it was stage four lung cancer. He cannot walk because of the imbalance from the neuroma. He got facial paralysis from the neuroma. He lost hearing which is permanent after cyber knifing the neuroma. Can’t eat because of the facial paralysis can’t see out of the eye with the facial paralysis can’t speak he had the most beautiful Barry White voice which has been gone since last year. It’s just crazy. I can’t believe this all happened to him and nobody caught any of this. I still will never believe that you can go to stage 4 with no indication and not know any of the numbers in between no one will ever convince me of that. I just believe that all these people were taking their share and not paying attention, but that being the case I’m just worried about the eating right now and the hydration. Anyone have any thoughts?