Hi Anne,
My dad is in a similar situation. He has bladder cancer which has metastasized to the bones. He has had chemo and radiation therapy. Every few days, he suffers from cancer pain which leaves him weaker than before. It is sort of like a vicious cycle which leaves him weaker. He can't walk that much which is causing muscle atrophy. Because of his weakness, he can't fight the pain that well. He is taking morphine and some other pain killers for pain relief.
I'm sure you've already seen this website but it has a lot of info about cancer-pain and is promising.
www.cancer-pain.org . According to this website, cancer-pain can almost always be relieved. If you haven't already consulted with them, it might be worth it to consult a pain management clinic. These have anesthesiologists who use different methods to control the pain, including nerve blocks etc (more info in the aforementioned website).
My dad has also just started drinking Ensure to make up for the deficiencies in his diet and since he did, the pain hasn't been that severe. I can not conclusively say that drinking Ensure has helped him manage his pain better because of the short duration but I hope that he doesn't suffer such pains again. It is terrible to witness let alone suffer from it. A good diet during this disease is always recommended.
I noticed that your post was earlier in the year. Hopefully, your husband has overcome his pain already. If so, please share what helped him overcome his pain.
best,
~ Mo