My treatment consisted of 14 weeks of chemotherapy, with radiation the last 7. A couple of weeks into the radiation, I began to feel very spaced out, almost in a twilight zone. And I wasn't taking any painkillers. Much of the time, I just wanted to be left alone.

I think the total treatment experience is very disorienting. I did gradually come out of it after treatment ended, and now 9 months later I feel much more like my old self. So I would expect your Dad to bounce back some, but it probably will be slow going.