Hi Kelly, I don't quite understand what the doctor meant about your dad getting a second cancer.It is always very important to get enough in the body during treatment to fight the battle. I remember during my radiation, my oncologist admitted me to hospital and suggested tube feeding when I lost 10 pounds (of course the figure may vary from different patients because I wasn't that heavy to begin with and 10 pounds means a lot to me.) It was myself who begged him to let me try eating. While I felt lucky of not having a tube inserted and be able to take enough nutrients I needed, you really have to be pushy and discuss your concern over your Dad's weak body to the doctors. Hope everything turns out fine.
Karen.