If I were in your position, I would be taking my mother for a second opinion. The pain is something she shouldn't have to deal with, nor the fistula. To much "we don't know" going on with her doctors so it's time to find someone that is experienced with her issues. Good luck with it.
Minnie

SCC Left Mandible. Jaw replaced with bone from leg. Neck disection, 37 radiation treatments. Recurrence 8-28-07, stage 2, tongue. One third of tongue removed 10-4-07. 5-23-08 chemo started for tumor behind swallowing passage, Our good friend and much loved OCF member Minnie has been lost to the disease (RIP 10-29-08). We will all miss her greatly.