These questions come to mind. How many calories is he getting each day? Weight loss while it could be an indication of something more, can be as simple as not getting 2000+ calories a day. So look at the most basic reason for weight loss first. This lack of good nutrition may also make for a feeling of being lethargic as well. In my own case I had about one month of recovery for every week of radiation. I actually got worse for the first two months after treatment ended...radiation sickness. I was on morphine and other pseudo morphines for almost 10 months after treatment. These made me want to sleep all the time and I had 0 energy. He is still on strong pain relievers and this may be a contributing factor in how things are going. Lastly, I had severe withdrawls as my morphine began to be reduced, as I had been on heavy doses for over a year. That included alternating fever and chills and sweats to go with them. Until the tissues of my sinus area began to recover from the radiation damage, the mucous flowed.... tons of mucous makes me want to throw up. I do not know if his situation is paralleling mine or something else is a play. When in doubt you can always get a second opinion to catch any doctors that are missing clues to something serious. I hope that is not the case, and ask that you keep a calorie and nutrition DAILY LOG for a few weeks. Also to speak with your doctors individually about the points that I mentioned and his condition.