I was in the same shape as your dad although he does have 30+ years on me. I wanted to quit & was "coached" through & continued till the end. It is the hardest thing I have ever done in my whole life! I resisted taking my pain meds & was a real rebel all the way through! Everybody goes through differently. As long as he finishes. The chances are better statistically if he completes the rad. Tell him I said it can be done, it just sucks for a while. Erik