Robyn,
It sounds like a good MRI result to me. I hope something develops with that throat nerve, that seems to be the main remaining hurdle for Eric.
I would not worry about the scar tissue, which is what it most likely is. It would take some time to start regrowing, if it ever does; and even then, maybe a little zap of radiation would finish it off. It is very unlikely to become a big deal. OMG16's son, who has had plenty to worry about at his young age, told her one time "No sense in worrying until you have something to worry about."
I agree with your comment about university settings, the academic world is a good place for medicine, with lots of good minds, and lots of cross-checking and paying attention to details. They can be busy and hectic, but the care is as good as it gets.
Best wishes to you and Eric,
Steve