Michael Douglas is doing promotion for Wall St. 2 despite facing a tough personal battle with throat cancer, with which he was diagnosed just three weeks ago. He appeared on Letterman last night, where he joked that he learned he had cancer on the same day he was booked for the show. He looks great but you can tell that he’s thinner and that his voice is a little hoarse and has changed. Douglas said that he’s done one week of radiation and chemotherapy for the tumor, which has not spread, and that he has stage four cancer, with an 80% chance of recovery or higher.

As for how he found out, he said he had a “sore throat early in the summer. I actually went through a litany of doctors and tests and they didn’t find anything. Then I had a great summer after some other adversities and all that. A wonderful summer with Catherine and the kids. We were in Spain. They really liked Americans in Europe this year, it’s nice…. Went to Russia, St. Petersburg. But I came back… got a biopsy, it’s a stage four, which is intense. They gotta go at it.

The things that change… is the chemotherapy in terms of being able to deal with the nausea. They knock you out pretty hard.”

Dave asked “Is stage four where you want to be?”

“No, you’d like to be down on stage one… The big thing you’re always worried about is spreading. I am head and neck. Nothing has gone down and the expectations are good. This is going to cut into the foreign promotional tour for Wall St. at least.”

As for why Douglas doesn’t sound like he has throat cancer or look sick, he joked that he was “pretty lit up right now” and added later “I’m on stage [performing].” He did acknowledge that he has a tough road ahead of him.

“This is the first week, and the chemo and the radiation continues to burn your mouth. It becomes more difficult to swallow, you can’t take solids.”

Dave asked about his chances of recovery, and Michael put it at 80% with some hospitals giving him better odds.

Dave then asked what he could do for Michael and he said “Give me a hug!”

The two guys embraced and it was really sweet.

Hang in there, Michael! We love to see you and to hear you’re ok, but you don’t have to go running around on a promotional tour. Focus on your recovery and we’ll be rooting for you. We still reserve the right to make fun of your hair though, ok?

Update: Michael is on the cover of this week’s People Magazine. People has an excerpt from their exclusive interview with Douglas and his wife, Catherine Zeta Jones. Jones says it’s the first time she’s ever really seen him get tired. Douglas calls his treatment “a fight” and adds that “it really knocks you out.”