Former President Jimmy Carter announced Thursday that cancer first discovered on his liver has spread to his brain and he's starting treatment.

FOX News Radio's Jon Decker in Washington has more:

Speaking at the Carter Center in Atlanta, former President Jimmy Carter announced that although a recent operation was successful in removing cancer from his liver, the cancer has spread to four spots in his brain.

(Carter) "They are very small spots... about two millimeters, if you can envision what a millimeter is... and I'll get my first radiation treatment for the melanoma in my brain this afternoon."

Carter, who is 90 years old, will follow that up with three more chemotherapy sessions in three week intervals. The 39th President has remained very active in his humanitarian work since his reelection defeat in 1980. He says that he's upbeat about what lies ahead in the next few months.