I am so sorry you are experiencing such misery. My husband had bladder cancer but had little pain with it, a different type than yours. My experience with head and neck cancer and radiation included oral pain after radiation. Dexamethasone was helpful in quieting the inflammation. My experience as a veterinarian says that your long term pain has been "amped up" by your nervous system, as chronic pain seems to sensitize nerves to increase the pain sensations. If the steroid and hydro do not relieve you enough, I would recommend a pain management specialist who may use things like a TENS unit or drugs like Gabapentin or Amantadine to help block the pain signals. Keep seeking out the experts until you get relief. I am sure Mayo has an excellent Pain Management team. Good luck .