Shannon:
With my radiation, once my treatments were done, I had received the max amount of radiation I can get in my lifetime, in that area. Treatment is finished. They successfully turned my right lung into a 'crispy critter' Oh, and they slapped the heck out of the tumor while they were at it. It wasn't fun, I grew to love macaroni and cheese and other soft foods while I was going through it, but it did what it was supposed to do; I've been stable for the year since my treatment ended.
Hopefully, your dad's treatment will be successful.
Oliver