My brother's came back in three weeks following surgery. They didn't do a cat scan for another month, but his pain started again after three weeks and I know in my heart that the pain was a sign of the cancer because it was not "normal" for it to come back like it did. I wish I had more answers for you, but I do agree that your father will need help. These surgeries are tramatic both physically and emotionally and I can't imagine someone going through it alone. I'm sure it can be done, but not if it is in anyway avoidable.
Best of luck, I'll keep my fingers crossed,