He did have a disease. The treatment causes weakness. Weakness can only get better when you do things to make you stronger. Bedrest begets bedrest. I began with walking. ( walking in a pool is good) Every two days I increased my distance. Qigong is a healing form of Tai Chi. Start the class slowly until you can stay the whole class. The weakness will resolve. Be sure he is taking his Vitamin D. Protein shakes are helpful. Also Lymphoma is classed different than other diseases. His stage 4 just means how many nodes are involved. I would work on mindset to help him heal. The book Cancer, Stress and mindset makes a difference.

I feel the same way at times with my lymphoma, tired and not much energy. I am here for him if he wants to correspond. Janet Gray