"They said that it's very serious, that the prognosis is very, very serious," the 81-year-old McCain, R-Ariz., said during the segment titled "The Fighter."
"Some say 3%, some say 14%. You know, it's a very poor prognosis," he continued. "So I just said, 'I understand. Now we're gonna do what we can, get the best doctors we can find and do the best we can.'
"And, at the same time, celebrate, with gratitude, a life well-lived."
McCain, a former naval aviator who was shot down over North Vietnam in 1967 and held as a prisoner of war until 1973, also revealed that he wants his memorial service held at his alma mater in Annapolis, Md.
"I want, when I leave, that the ceremony is at the Naval Academy," he said. "And we just have a couple of people that stand up and say, 'This guy, he served his country.'"