"The Late Show with David Letterman" welcomes actor Michael Douglas on Tuesday night (Aug. 31), wherein Douglas expresses optimism about his throat cancer diagnosis.Douglas reveals that he just finished his first week of radiation and chemotherapy and that "it's about an eight-week struggle.""This all happened within three weeks, and got a biopsy and they analyzed it - it's a stage 4, which is intense, and so they've got to go at it," Douglas continues. Letterman asks, "Now when you said stage 4, I heard someone gasp. Now, is stage 4 where you want to be or where you not want to be?"Douglas said, "Um, no. No, you like to be down at stage 1 ... but it has not - the big thing you're always worried about is it spreading, so I am head and neck. I am above the neck, so nothing's gone down, and the expectations are good."Watch the interview clip below for more of the piece.