The "Wall Street" star said he’s undergone the first of eight weeks of chemo and radiation therapy and doctors say he has an 80 percent shot at a full recovery from throat cancer.
Douglas, whose latest film “Wall Street: Money Never Sleeps” is set to open Sept. 24, joked that he came down with cancer to see “how far I would go to promote a movie.”
"You've never looked better to me, and this proves that you're a tough guy, for God's sakes,” Letterman said to much applause from the crowd.
"Let's just say ... I'm pretty lit up right now," Douglas replied.
Douglas said he experienced a sore throat around the beginning of summer, but his doctors only determined months later that he had stage-four cancer, “which is intense,” he said.
“You like to be down at stage one,” Douglas explained, but added that he was optimistic because the disease had not spread.
“You don’t sound like you have throat cancer,” Letterman said. “Why is that?”
“Because I’m on stage,” Douglas shot back. "It hurts, it comes in waves."
Radiation treatment burns his lips, while chemotherapy “knocks you out really hard,” Douglas said.
"Did they find it early enough for their liking?" Letterman asked.
"I sure as s--- hope so," Douglas said.
Despite the cancer, Douglas said he had a very good summer with his wife, actress Catherine Zeta-Jones, and his children traveling in Spain and Russia.
"Wow, boy, I feel like I want to do something for you. Can I do something for you?" Letterman asked as the interview wrapped up.
"Aww, give me a hug," Douglas said as he stood up to receive Letterman’s embrace.