Michael Douglas Battles Stage 4 Throat Cancer

Stage four cancer is defined as a cancer that has spread to other parts of the body.

The 65-year-old "Wall Street" star told David Letterman Tuesday night, however, that his cancer has not spread to the rest of his body and is therefore still treatable. He appeared on "Late Show" to promote his coming film, "Wall Street: Money Never Sleeps."

Asked about the severity of his condition, Douglas told Letterman "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."

Douglas is undergoing radiation and chemotherapy. He said he has completed week one of the eight week regimen.